Vitamin D Deficiency

Vitamin D Deficiency Testing and health information

You can order a blood test to measure your levels of vitamin D directly with Ulta Lab Tests. The Vitamin D, 25-Hydroxy, Total and the Vitamin D, 25-Hydroxyvitamin D (D2, D3), LC/MS/MS (QuestAssureD™) are the most common test, followed by the Vitamin D, 1,25-Dihydroxy, LC/MS/MS test.

SEE BELOW THE LIST OF TESTS FOR MORE INFORMATION ABOUT  Guide On Vitamin D Testing


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Brief Description: A Vitamin D test is a blood test used to determine if you have a Vitamin D deficiency and to monitor Vitamin D levels if you are on supplementation.

Also Known As: Ergocalciferol Test, Vitamin D2 Test, Cholecalciferol Test, Vitamin D3 Test, Calcidiol Test, 25-hydroxyvitamin D Test, Calcifidiol Test, 25-hydroxy-vitamin D Test, Vitamin D Total Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: Fasting preferred, but not required.

When is a Vitamin D test ordered?

When calcium levels are inadequate and/or a person exhibits symptoms of vitamin D deficiency, such as rickets in children and bone weakening, softness, or fracture in adults, 25-hydroxyvitamin D is frequently ordered to rule out a vitamin D deficit.

When a person is suspected of having a vitamin D deficiency, the test may be requested. Vitamin D deficiency is more common in older folks, people who are institutionalized or homebound and/or have minimal sun exposure, people who are obese, have had gastric bypass surgery, and/or have fat malabsorption. People with darker skin and breastfed babies are also included in this category.

Before starting osteoporosis medication, 25-hydroxyvitamin D is frequently requested.

What does a Vitamin D blood test check for?

Vitamin D is a group of chemicals that are necessary for the healthy development and growth of teeth and bones. The level of vitamin D in the blood is determined by this test.

Vitamin D is tested in the blood in two forms: 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The primary form of vitamin D found in the blood is 25-hydroxyvitamin D, which is a relatively inactive precursor to the active hormone 1,25-dihydroxyvitamin D. 25-hydroxyvitamin D is routinely evaluated to assess and monitor vitamin D status in humans due to its longer half-life and higher concentration.

Endogenous vitamin D is created in the skin when exposed to sunshine, whereas exogenous vitamin D is taken through foods and supplements. Vitamin D2 and vitamin D3 have somewhat different molecular structures. Fortified foods, as well as most vitamin preparations and supplements, include the D2 form. The type of vitamin D3 produced by the body is also used in some supplements. When the liver and kidneys convert vitamin D2 and D3 into the active form, 1,25-dihydroxyvitamin D, they are equally effective.

Some tests may not differentiate between the D2 and D3 forms of vitamin D and just report the total result. Newer methods, on the other hand, may record D2 and D3 levels separately and then sum them up to get a total level.

Vitamin D's major function is to assist balance calcium, phosphorus, and magnesium levels in the blood. Vitamin D is necessary for bone growth and health; without it, bones become fragile, misshapen, and unable to mend themselves properly, leading to disorders such as rickets in children and osteomalacia in adults. Vitamin D has also been proven to influence the growth and differentiation of a variety of other tissues, as well as to aid in immune system regulation. Other illnesses, such as autoimmune and cancer, have been linked to vitamin D's other roles.

According to the Centers for Disease Control and Prevention, two-thirds of the US population has adequate vitamin D, while one-quarter is at risk of inadequate vitamin D and 8% is at risk of insufficiency, as defined by the Institute of Medicine's Dietary Reference Intake.

The elderly or obese, persons who don't receive enough sun exposure, people with darker skin, and people who take certain drugs for lengthy periods of time are all at risk of insufficiency. Adequate sun exposure is usually defined as two intervals of 5-20 minutes each week. Vitamin D can be obtained through dietary sources or supplements by people who do not get enough sun exposure.

This test has 3 Biomarkers

  • Vitamin D Total which is a combined measurement of Vitamin D, 25-Oh, D2 and Vitamin 25-Oh, D3
  • Vitamin D, 25-Oh, D2 which is a measurement of ergocalciferol Vitamin D, which is Vitamin D obtained through plant sources. 
  • Vitamin D, 25-Oh, D3 which is a measurement of cholecalciferol Vitamin D, which is Vitamin D obtained through animal sources.

Lab tests often ordered with a Vitamin D test:

  • Complete Blood Count
  • CMP
  • Iron and TIBC
  • Calcium
  • Phosphorus
  • PTH
  • Magnesium

Conditions where a Vitamin D test is recommended:

  • Kidney Disease
  • Osteoporosis
  • Lymphoma
  • Cystic Fibrosis
  • Autoimmune Disorders
  • Celiac Disease
  • Malabsorption
  • Malnutrition

Commonly Asked Questions:

How does my health care provider use a Vitamin D test?

Determine whether a deficit or excess of vitamin D is causing bone weakening, deformity, or improper calcium metabolism.

Because PTH is required for vitamin D activation, it can aid in diagnosing or monitoring problems with parathyroid gland function.

Because vitamin D is a fat-soluble vitamin that is absorbed from the intestine like a fat, it can help monitor the health of people with conditions that interfere with fat absorption, such as cystic fibrosis and Crohn's disease.

People who have had gastric bypass surgery and may not be able to absorb adequate vitamin D should be closely monitored.

When vitamin D, calcium, phosphorus, and/or magnesium supplementation is suggested, it can help assess the success of the treatment.

What do my Vitamin D results result mean?

Despite the fact that vitamin D techniques differ, most laboratories use the same reference intervals. Because toxicity is uncommon, researchers have focused on the lower limit and what cut-off for total 25-hydroxyvitamin D shortage implies.

A low blood level of 25-hydroxyvitamin D could indicate that a person isn't getting enough sunlight or dietary vitamin D to meet his or her body's needs, or that there's an issue with absorption from the intestines. Seizure medications, notably phenytoin, might occasionally interfere with the liver's generation of 25-hydroxyvitamin D.

Vitamin D insufficiency has been linked to an increased risk of some malignancies, immunological illnesses, and cardiovascular disease.

Excessive supplementation with vitamin pills or other nutritional supplements frequently results in a high level of 25-hydroxyvitamin D.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


Description: A Vitamin D test is a blood test used to determine if you have a Vitamin D deficiency and to monitor Vitamin D levels if you are on supplementation. 

Also Known As: 25-hydroxyvitamin D Test, Vitamin D 25-Hydroxyvitamin Test 

Collection Method: Blood Draw 

Specimen Type: Serum 

Test Preparation: Fasting preferred, but not required. 

When is a Vitamin D test ordered?

When calcium levels are inadequate and/or a person exhibits symptoms of vitamin D deficiency, such as rickets in children and bone weakening, softness, or fracture in adults, 25-hydroxyvitamin D is frequently ordered to rule out a vitamin D deficit. 

When a person is suspected of having a vitamin D deficiency, the test may be requested. Vitamin D deficiency is more common in older folks, people who are institutionalized or homebound and/or have minimal sun exposure, people who are obese, have had gastric bypass surgery, and/or have fat malabsorption. People with darker skin and breastfed babies are also included in this category. 

Before starting osteoporosis medication, 25-hydroxyvitamin D is frequently requested. 

What does a Vitamin D blood test check for? 

Vitamin D is a group of chemicals that are necessary for the healthy development and growth of bones and teeth. The level of vitamin D in the blood is determined by this test. 

Vitamin D is tested in the blood in two forms: 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The primary form of vitamin D found in the blood is 25-hydroxyvitamin D, which is a relatively inactive precursor to the active hormone 1,25-dihydroxyvitamin D. 25-hydroxyvitamin D is routinely evaluated to assess and monitor vitamin D status in humans due to its longer half-life and higher concentration. 

Vitamin D's major function is to assist balance calcium, phosphorus, and magnesium levels in the blood. Vitamin D is necessary for bone growth and health; without it, bones become fragile, misshapen, and unable to mend themselves properly, leading to disorders such as rickets in children and osteomalacia in adults. Vitamin D has also been proven to influence the growth and differentiation of a variety of other tissues, as well as to aid in immune system regulation. Other illnesses, such as autoimmune and cancer, have been linked to vitamin D's other roles. 

According to the Centers for Disease Control and Prevention, two-thirds of the US population has adequate vitamin D, while one-quarter is at risk of inadequate vitamin D and 8% is at risk of insufficiency, as defined by the Institute of Medicine's Dietary Reference Intake. 

The elderly or obese, persons who don't receive enough sun exposure, people with darker skin, and people who take certain drugs for lengthy periods of time are all at risk of insufficiency. Adequate sun exposure is usually defined as two intervals of 5-20 minutes each week. Vitamin D can be obtained through dietary sources or supplements by people who do not get enough sun exposure. 

Lab tests often ordered with a Vitamin D test: 

  • Complete Blood Count 
  • CMP 
  • Iron and TIBC 
  • Calcium 
  • Phosphorus 
  • PTH 
  • Magnesium

Conditions where a Vitamin D test is recommended:

  • Kidney Disease 
  • Osteoporosis 
  • Lymphoma 
  • Cystic Fibrosis 
  • Autoimmune Disorders 
  • Celiac Disease 
  • Malabsorption 
  • Malnutrition 

Commonly Asked Questions: 

How does my health care provider use a Vitamin D test? 

Determine whether a deficit or excess of vitamin D is causing bone weakening, deformity, or improper calcium metabolism. 

Because PTH is required for vitamin D activation, it can aid in diagnosing or monitoring problems with parathyroid gland function. 

Because vitamin D is a fat-soluble vitamin that is absorbed from the intestine like a fat, it can help monitor the health of people with conditions that interfere with fat absorption, such as cystic fibrosis and Crohn's disease. 

People who may not be able to absorb vitamin D adequately or have had gastric bypass surgery should be closely monitored. 

When vitamin D, calcium, phosphorus, and/or magnesium supplementation is suggested, it can help assess the success of the treatment. 

What do my Vitamin D results result mean? 

Even though vitamin D techniques differ, most laboratories use the same reference intervals. Because toxicity is uncommon, researchers have focused on the lower limit and what cut-off for total 25-hydroxyvitamin D shortage implies. 

A low blood level of 25-hydroxyvitamin D could indicate that a person isn't getting enough sunlight or dietary vitamin D to meet his or her body's needs, or that there's an issue with absorption from the intestines. Seizure medications, notably phenytoin, might occasionally interfere with the liver's generation of 25-hydroxyvitamin D. 

Vitamin D insufficiency has been linked to an increased risk of some malignancies, immunological illnesses, and cardiovascular disease. 

Excessive supplementation with vitamin pills or other nutritional source of vitamin D frequently results in a high level of 25-hydroxyvitamin D. 

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


Description: A Vitamin D test is a blood test used to determine if you have a Vitamin D deficiency and to monitor Vitamin D levels if you are on supplementation.

Also Known As: Ergocalciferol Test, Vitamin D2 Test, Cholecalciferol Test, Vitamin D3 Test, Calcidiol Test, 25-hydroxyvitamin D Test, Calcifidiol Test, 25-hydroxy-vitamin D Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: Fasting preferred, but not required.

When is a Vitamin D test ordered:

When calcium levels are inadequate and/or a person exhibits symptoms of vitamin D deficiency, such as rickets in children and bone weakening, softness, or fracture in adults, 25-hydroxyvitamin D is frequently ordered to rule out a vitamin D deficit.

When a person is suspected of having a vitamin D deficiency, the test may be requested. Vitamin D deficiency is more common in older folks, people who are institutionalized or homebound and/or have minimal sun exposure, people who are obese, have had gastric bypass surgery, and/or have fat malabsorption. People with darker skin and breastfed babies are also included in this category.

Before starting osteoporosis medication, 25-hydroxyvitamin D is frequently requested.

What does a Vitamin D blood test check for?

Vitamin D is a group of chemicals that are necessary for the healthy development and growth of teeth and bones. The level of vitamin D in the blood is determined by this test.

Vitamin D is tested in the blood in two forms: 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The primary form of vitamin D found in the blood is 25-hydroxyvitamin D, which is a relatively inactive precursor to the active hormone 1,25-dihydroxyvitamin D. 25-hydroxyvitamin D is routinely evaluated to assess and monitor vitamin D status in humans due to its longer half-life and higher concentration.

Endogenous vitamin D is created in the skin when exposed to sunshine, whereas exogenous vitamin D is taken through foods and supplements. Vitamin D2 and vitamin D3 have somewhat different molecular structures. Fortified foods, as well as most vitamin preparations and supplements, include the D2 form. The type of vitamin D3 produced by the body is also used in some supplements. When the liver and kidneys convert vitamin D2 and D3 into the active form, 1,25-dihydroxyvitamin D, they are equally effective.

Some tests may not differentiate between the D2 and D3 forms of vitamin D and just report the total result. Newer methods, on the other hand, may record D2 and D3 levels separately and then sum them up to get a total level.

Vitamin D's major function is to assist balance calcium, phosphorus, and magnesium levels in the blood. Vitamin D is necessary for bone growth and health; without it, bones become fragile, misshapen, and unable to mend themselves properly, leading to disorders such as rickets in children and osteomalacia in adults. Vitamin D has also been proven to influence the growth and differentiation of a variety of other tissues, as well as to aid in immune system regulation. Other illnesses, such as autoimmune and cancer, have been linked to vitamin D's other roles.

According to the Centers for Disease Control and Prevention, two-thirds of the US population has adequate vitamin D, while one-quarter is at risk of inadequate vitamin D and 8% is at risk of insufficiency, as defined by the Institute of Medicine's Dietary Reference Intake.

The elderly or obese, persons who don't receive enough sun exposure, people with darker skin, and people who take certain drugs for lengthy periods of time are all at risk of insufficiency. Adequate sun exposure is usually defined as two intervals of 5-20 minutes each week. Vitamin D can be obtained through dietary sources or supplements by people who do not get enough sun exposure.

This test has 3 Biomarkers

  • Vitamin D Total which is a combined measurement of Vitamin D, 25-Oh, D2 and Vitamin 25-Oh, D3
  • Vitamin D, 25-Oh, D2 which is a measurement of ergocalciferol Vitamin D, which is Vitamin D obtained through plant sources. 
  • Vitamin D, 25-Oh, D3 which is a measurement of cholecalciferol Vitamin D, which is Vitamin D obtained through animal sources.

Lab tests often ordered with a Vitamin D test:

  • Complete Blood Count
  • CMP
  • Iron and TIBC
  • Calcium
  • Phosphorus
  • PTH
  • Magnesium

Conditions where a Vitamin D test is recommended:

  • Kidney Disease
  • Osteoporosis
  • Lymphoma
  • Cystic Fibrosis
  • Autoimmune Disorders
  • Celiac Disease
  • Malabsorption
  • Malnutrition

Commonly Asked Questions:

How does my health care provider use a Vitamin D test?

Determine whether a deficit or excess of vitamin D is causing bone weakening, deformity, or improper calcium metabolism.

Because PTH is required for vitamin D activation, it can aid in diagnosing or monitoring problems with parathyroid gland function.

Because vitamin D is a fat-soluble vitamin that is absorbed from the intestine like a fat, it can help monitor the health of people with conditions that interfere with fat absorption, such as cystic fibrosis and Crohn's disease.

People who have had gastric bypass surgery and may not be able to absorb adequate vitamin D should be closely monitored.

When vitamin D, calcium, phosphorus, and/or magnesium supplementation is suggested, it can help assess the success of the treatment.

What do my Vitamin D results result mean?

Despite the fact that vitamin D techniques differ, most laboratories use the same reference intervals. Because toxicity is uncommon, researchers have focused on the lower limit and what cut-off for total 25-hydroxyvitamin D shortage implies.

A low blood level of 25-hydroxyvitamin D could indicate that a person isn't getting enough sunlight or dietary vitamin D to meet his or her body's needs, or that there's an issue with absorption from the intestines. Seizure medications, notably phenytoin, might occasionally interfere with the liver's generation of 25-hydroxyvitamin D.

Vitamin D insufficiency has been linked to an increased risk of some malignancies, immunological illnesses, and cardiovascular disease.

Excessive supplementation with vitamin pills or other nutritional supplements frequently results in a high level of 25-hydroxyvitamin D.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


Vitamin D & K Panel contains: Vitamin D, 25-Hydroxyvitamin D (D2, D3), LC/MS/MS (QuestAssureD™) and Vitamin K.


Vitamin D Panel contains: Vitamin D, 25-Hydroxyvitamin D (D2, D3), LC/MS/MS (QuestAssureD™) and  Vitamin D, 1,25-Dihydroxy, LC/MS/MS


Measurement of serum 25-OH vitamin D concentrations provide a good index of circulating vitamin D activity in patients not suffering from renal disease. Lower than normal 25-OH vitamin D levels can result from a dietary deficiency, poor absorption of the vitamin or impaired metabolism of the sterol in the liver. A 25-OH vitamin D deficiency can lead to bone diseases such as rickets and osteomalacia. Above normal levels can lead hypercalcemia. This assay employs liquid chromatography tandem mass spectrometry to independently measure and report the two common forms of 25-hydroxy vitamin D: 25OH D3 - the endogenous form of the vitamin and 25OH D2 - the analog form used to treat 25OH Vitamin D3 deficiency. While this assay will produce accurate Vitamin D results on patients of any age, it is specifically indicated for infants less than 3 years of age.


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Description: A Calcium test is a blood test that is used to screen for, diagnose, and monitor a wide range of medical conditions.

Also Known As: Ca Test, Serum Calcium Test, Calcium Blood Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a Calcium test ordered?

A blood calcium test is frequently requested during a general medical evaluation. It's usually part of the comprehensive metabolic panel or the basic metabolic panel, two sets of tests that can be done during an initial evaluation or as part of a routine medical checks.

Many people do not experience symptoms of high or low calcium until their levels are dangerously high or low.

When a person has certain types of cancer, kidney illness, or has had a kidney transplant, calcium monitoring may be required. When someone is being treated for abnormal calcium levels, monitoring may be required to determine the effectiveness of medications such as calcium or vitamin D supplements.

What does a Calcium blood test check for?

Calcium is one of the most plentiful and vital minerals in the human body. It is required for cell signaling as well as the proper operation of muscles, nerves, and the heart. Calcium is essential for blood clotting as well as bone growth, density, and maintenance. This test determines how much calcium is present in the blood.

Calcium is found complexed in the bones for 99 percent of the time, while the remaining 1% circulates in the blood. Calcium levels are closely monitored; if too little is absorbed or consumed, or if too much is lost through the kidney or stomach, calcium is removed from bone to keep blood concentrations stable. Approximately half of the calcium in the blood is metabolically active and "free." The other half is "bound" to albumin, with a minor proportion complexed to anions like phosphate, and both of these forms are metabolically inactive.

Blood calcium can be measured using two different tests. The free and bound forms of calcium are measured in the total calcium test. Only the free, physiologically active form of calcium is measured in the ionized calcium test.

Lab tests often ordered with a Calcium test:

  • Phosphorus
  • Vitamin D
  • Magnesium
  • PTH
  • Albumin
  • Basic Metabolic Panel (BMP)
  • Comprehensive Metabolic Panel (CMP)

Conditions where a Calcium test is recommended:

  • Kidney Disease
  • Thyroid Disease
  • Alcoholism
  • Malnutrition
  • Parathyroid Diseases
  • Breast Cancer
  • Multiple Myeloma

How does my health care provider use a Calcium test?

A blood calcium test is used to screen for, diagnose, and monitor a variety of bone, heart, nerve, kidney, and tooth disorders. If a person has signs of a parathyroid disease, malabsorption, or an overactive thyroid, the test may be ordered.

A total calcium level is frequently checked as part of a standard health check. It's part of the comprehensive metabolic panel and the basic metabolic panel, which are both collections of tests used to diagnose or monitor a range of ailments.

When a total calcium result is abnormal, it is interpreted as a sign of an underlying disease. Additional tests to assess ionized calcium, urine calcium, phosphorus, magnesium, vitamin D, parathyroid hormone, and PTH-related peptide are frequently performed to assist determine the underlying problem. PTH and vitamin D are in charge of keeping calcium levels in the blood within a narrow range of values.

Measuring calcium and PTH combined can assist identify whether the parathyroid glands are functioning normally if the calcium is abnormal. Testing for vitamin D, phosphorus, and/or magnesium can assist evaluate whether the kidneys are excreting the right amount of calcium, and measuring urine calcium can help detect whether additional deficits or excesses exist. The balance of these many compounds is frequently just as critical as their concentrations.

The total calcium test is the most common test used to determine calcium status. Because the balance between free and bound calcium is usually constant and predictable, it is a reliable reflection of the quantity of free calcium present in the blood in most cases. However, the balance between bound and free calcium is altered in some persons, and total calcium is not a good indicator of calcium status. Ionized calcium measurement may be required in certain cases. Critically sick patients, those receiving blood transfusions or intravenous fluids, patients undergoing major surgery, and persons with blood protein disorders such low albumin are all candidates for ionized calcium testing.

What do my Calcium test results mean?

The amount of calcium circulating in the blood is not the same as the amount of calcium in the bones.

A feedback loop including PTH and vitamin D regulates and stabilizes calcium uptake, utilization, and excretion. Conditions and disorders that disturb calcium control can induce abnormal acute or chronic calcium elevations or declines, resulting in hypercalcemia or hypocalcemia symptoms.

Total calcium is usually tested instead of ionized calcium since it is easier to do and requires no additional treatment of the blood sample. Because the free and bound forms of calcium make up about half of the total, total calcium is usually a decent depiction of free calcium. Because nearly half of the calcium in blood is bonded to protein, high or low protein levels might alter total calcium test findings. In these circumstances, an ionized calcium test is more appropriate for measuring free calcium.

A normal total or ionized calcium test, when combined with other normal laboratory findings, indicates that a person's calcium metabolism is normal and blood levels are properly managed.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


Urinary calcium reflects dietary intake, rate of calcium absorption by the intestine and bone resorption. Urinary calcium is used primarily to evaluate parathyroid function and the effects of vitamin D. A significant number of patients with primary hyperparathyroidism will have elevated urinary calcium. However, there are other clinical entities that may be associated with increased urine calcium: Sarcoidosis, Paget's disease of bone, vitamin D intoxication, hyperthyroidism and glucocorticoid excess. Decreased urine calcium is seen with thiazide diuretics, vitamin D deficiency and familial hypocalciuric hypercalcemia.

Description: A Phosphate or phosphorus test is a blood test that measures the level of phosphorus in your blood’s serum to screen for conditions associated with abnormal phosphorus levels such as kidney, liver, and bone disease.

Also Known As: Inorganic Phosphate Test, P Test, Phosphate as Phosphorus Test, Phosphorus Test, Phosphate Test, PO4 Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a Phosphate test ordered?

Because modestly elevated phosphorus levels normally do not induce symptoms, phosphorus testing is usually done after an abnormal calcium test and/or when signs of abnormal calcium, such as fatigue, muscle weakness, cramps, or bone issues, are evident.

When symptoms suggest kidney or gastrointestinal problems, phosphorus testing may be recommended in conjunction with other tests.

Testing for both phosphorus and calcium levels may be conducted at regular intervals to assess therapy effectiveness when problems causing abnormal phosphorus and/or calcium levels are discovered.

When a person develops diabetes or shows signs of an acid-base imbalance, their phosphorus levels may be monitored.

What does a Phosphate blood test check for?

Phosphorus is a mineral that forms organic and inorganic phosphate compounds when it reacts with other elements. When it comes to testing, the terms phosphorus and phosphate are frequently interchanged, but a serum phosphorus/phosphate test measures the amount of inorganic phosphate in the blood.

Energy production, muscle and neuron function, and bone formation all require phosphorus. They also serve as a buffer, assisting in the maintenance of the body's acid-base equilibrium.

Phosphorus enters the body through the food we eat. It can be found in a wide variety of meals and is quickly absorbed by the intestines. About 70-80 percent of the phosphates in the body combine with calcium to help build bones and teeth, another 10% is located in muscle, and about 1% is found in nerve tissue. The rest can be found in cells all across the body, where they are mostly employed to store energy.

In normal circumstances, only about 1% of total body phosphates are found in the blood. Phosphorus is found in a wide range of foods, including beans, peas, and almonds, cereals, dairy products, eggs, meat, poultry, and fish. The body regulates how much phosphorus/phosphate it takes from the intestines and how much it excretes through the kidneys to maintain phosphorus/phosphate levels in the blood. The combination of parathyroid hormone, calcium, and vitamin D affects phosphate levels as well.

Malnutrition, malabsorption, acid-base imbalances, hypercalcemia, and illnesses that impact kidney function can all cause phosphorus shortages. Phosphorus excesses can occur as a result of high phosphorus ingestion, hypocalcemia, or kidney disease.

Often, a person with a mild to severe phosphorus deficit has no symptoms. Muscle weakness and disorientation are common symptoms of severe phosphorus insufficiency. Muscle cramps, confusion, and even convulsions can be caused by a severe excess of phosphorus, which is comparable to the symptoms of low calcium.

Lab tests often ordered with a Phosphate test:

  • Calcium
  • Complete Blood Count
  • Iron Total
  • Iron Total and Total Iron binding capacity
  • Magnesium
  • Comprehensive Metabolic Panel
  • Vitamin D
  • Parathyroid Hormone

Conditions where a Phosphate test is recommended:

  • Kidney Disease
  • Diabetes
  • Acidosis
  • Alkalosis
  • Hyperparathyroidism
  • Hypoparathyroidism
  • Malnutrition
  • Alcoholism
  • Hypothyroidism

How does my health care provider use a Phosphate test?

Phosphorus tests are frequently requested in conjunction with other tests, such as calcium, parathyroid hormone, and/or vitamin D, to aid in the diagnosis and/or monitoring of various calcium and phosphorus abnormalities.

While phosphorus tests are most typically done on blood samples, urine samples are sometimes used to evaluate phosphorus clearance by the kidneys.

What does my Phosphorus test result mean?

Hypophosphatemia can be caused by or linked to:

  • Hypercalcemia 
  • Diuretics overuse
  • Malnutrition
  • Alcoholism
  • Burns that are severe
  • Ketoacidosis in diabetics
  • Hypothyroidism
  • Hypokalemia
  • Use of antacids on a regular basis
  • Rickets and osteomalacia

Hyperphosphatemia can be caused by or linked to:

  • Failure of the kidneys
  • Hepatitis
  • Hypoparathyroidism
  • Ketoacidosis in diabetics
  • Phosphate supplementation

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


Description: Vitamin D, 1,25-Dihydroxy, LC/MS/MS is a blood test that measures calcitriol (1,25-Dihydroxyvitamin) in your blood's serum.

Also Known As: Calcitriol Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a Vitamin D 1,25-Dihydroxy test ordered?

When renal illness or problems of the enzyme that converts 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D are suspected, 1,25-dihydroxyvitamin D tests may be requested. This test is only performed in rare cases when calcium levels are high or a person has an illness that produces excessive amounts of vitamin D, such as sarcoidosis or some types of lymphoma.

Vitamin D levels are sometimes evaluated to check therapy success when vitamin D, phosphorus, calcium or magnesium supplementation is required.

What does a Vitamin D 1,25-Dihydroxy blood test check for?

Vitamin D is a group of chemicals that are necessary for the healthy development and growth of teeth and bones. The level of vitamin D in the blood is determined by this test.

Vitamin D is tested in the blood in two forms: 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The primary form of vitamin D found in the blood is 25-hydroxyvitamin D, which is a relatively inactive precursor to the active hormone 1,25-dihydroxyvitamin D. 25-hydroxyvitamin D is routinely evaluated to assess and monitor vitamin D status in humans due to its longer half-life and higher concentration.

Endogenous vitamin D is created in the skin when exposed to sunshine, whereas exogenous vitamin D is taken through foods and supplements. Vitamin D2 and vitamin D3 are two separate kinds of vitamin D with somewhat different chemical structures. Fortified foods, as well as most vitamin preparations and supplements, include the D2 form. The type of vitamin D3 produced by the body is also used in some supplements. When the liver and kidneys convert vitamin D2 and D3 into the active form, 1,25-dihydroxyvitamin D, they are equally effective.

Vitamin D's major function is to assist balance calcium, phosphorus, and magnesium levels in the blood. Vitamin D is necessary for bone growth and health; without it, bones become fragile, misshapen, and unable to mend themselves properly, leading to disorders such as rickets in children and osteomalacia in adults. Vitamin D has also been proven to influence the growth and differentiation of a variety of other tissues, as well as to aid in immune system regulation. Other illnesses, such as autoimmune and cancer, have been linked to vitamin D's other roles.

According to the Centers for Disease Control and Prevention, two-thirds of the US population has adequate vitamin D, while one-quarter is at risk of inadequate vitamin D and 8% is at risk of insufficiency, as defined by the Institute of Medicine's Dietary Reference Intake.

The elderly or obese, persons who don't receive enough sun exposure, people with darker skin, and people who take certain drugs for lengthy periods of time are all at risk of insufficiency. Adequate sun exposure is usually defined as two intervals of 5-20 minutes each week. Vitamin D can be obtained through dietary sources or supplements by people who do not get enough sun exposure.

Lab tests often ordered with a Vitamin D 1,25-Dihydroxy test:

  • Vitamin D 25-Hydroxy (D2 and D3)
  • Calcium
  • Phosphorus
  • PTH
  • Magnesium
  • Bone Markers
  • Trace Minerals

Conditions where a Vitamin D 1,25-Dihydroxy test is recommended:

  • Osteoporosis
  • Kidney Disease
  • Lymphoma
  • Autoimmune Disorders
  • Cystic Fibrosis
  • Celiac Disease
  • Malabsorption
  • Malnutrition

How does my health care provider use a Vitamin D 1,25-Dihydroxy test?

Determine whether a deficit or excess of vitamin D is causing bone weakening, deformity, or improper calcium metabolism.

Because PTH is required for vitamin D activation, it can aid in diagnosing or monitoring problems with parathyroid gland function.

Because vitamin D is a fat-soluble vitamin that is absorbed from the intestine like a fat, it can help monitor the health of people with conditions that interfere with fat absorption, such as cystic fibrosis and Crohn's disease.

People who have had gastric bypass surgery and may not be able to absorb adequate vitamin D should be closely monitored.

When vitamin D, calcium, phosphorus, and/or magnesium supplementation is suggested, it can help assess the success of the treatment.

What do my Vitamin D, 1,25-Dihydroxy test results mean?

In kidney illness, a low level of 1,25-dihydroxyvitamin D is one of the first alterations to appear in people with early renal failure.

A high amount of 1,25-dihydroxyvitamin D can arise when there is an excess of parathyroid hormone or when there are disorders that can produce 1,25-dihydroxyvitamin D outside of the kidneys, such as sarcoidosis or some lymphomas.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.


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Vitamin D Testing comes in two forms when found in the bloodstream: 1,25-dihydroxyvitamin D and 25-hydroxyvitamin D. Specialists concentrate on 25-hydroxyvitamin D when testing a person’s vitamin D levels because of it’s higher concentration and longer half-life. It is responsible for the development of healthy teeth and bones.

The human body can be exposed to vitamin D in two distinct manners – endogenous and exogenous.

Endogenous sources refer to general exposure to vitamin D, such as standing in the sunlight. In contrast, exogenous sources are ingested, such as food and supplements. The sources can vary when it comes to their chemical structures, which is why they are given different names. For example, vitamin D2 (ergocalciferol) is used to highlight plant-based types.

In contrast, vitamin D3 (cholecalciferol) is used to describe animal-based types. With vitamin D2, it is generally ingested through fortified foods, supplements, and/or vitamin preparations. On the other hand, vitamin D3 can be produced by the human body and/or ingested through supplements. When it comes to general efficiency, both vitamin D2 and D3 are efficient. They can easily be converted into 1,25-dihydroxyvitamin D by the liver.

The average test will not break down specific types of vitamin D. It will often refer to them as a singular unit. However, new-age testing methods are starting to incorporate intricate processes to help differentiate between D2 and D3 in the blood.

Vitamin D is responsible for regulating the amount of phosphorus, magnesium, and calcium found in the blood. Therefore, vitamin D is noted for its natural impact on the growth and formation of bones. If the body does not have enough vitamin D over a prolonged period, it can cause bones to soften, break down, or become malformed. As a result, people of all ages end up diagnosed with rickets or osteomalacia. Vitamin D is also noted for assisting with the immune system and strengthening the tissues. With reduced vitamin D levels, the body can become prone to conditions such as cancer and/or autoimmunity.

Research by the Centers for Disease Control and Prevention (CDC) mentions that approximately 25% of the American population is dealing with lower vitamin D levels. In comparison, 8% are noted to be at risk of vitamin D deficiency. It is important to note that the medical rating for “deficiency” is assigned by the Dietary Reference Intake (DRI).

Studies show that a person that’s elderly and/or has a higher BMI (body mass index) is far more prone to vitamin D deficiencies. This can also include individuals that have darker skin pigmentation, may not spend enough time in the sunlight, and/or take medications known for reducing the body’s vitamin D levels. It is necessary to spend at least 5-20 minutes (twice) in the sunlight. If a person is not getting enough sunlight, it is highly recommended to ingest vitamin D through food or supplements.

The Benefit of Getting Tested

It is essential to get out in front of a vitamin D deficiency while adjusting the amount of vitamin D being ingested.

When is it Best to Get Tested?

Vitamin D Testing should be performed as soon as there is a noticeable dip in a person’s phosphorus, parathyroid hormone, and/or calcium levels. This can signal towards an underlying bone condition or disease, which will worsen with a prolonged deficiency. These individuals are at risk of a vitamin D deficiency and should reach out to a qualified medical professional immediately. This test is required before a personalized treatment plan can be administered for osteoporosis. 

A vitamin D test offers:

  • A comprehensive analysis of any underlying bone malformations, bone weakness, and/or abnormalities in calcium/phosphorus/PTH, which is becoming pronounced due to a deficiency
  • Diagnosis of health-related problems associated with a dysfunctional parathyroid gland
  • Screening for individuals at risk of a vitamin D deficiency following the standards set by the National Osteoporosis Foundation and the Institute of Medicine
  • A health status update for relevant medical conditions such as Crohn’s disease and cystic fibrosis, which can cause issues with fat absorption in the human body
  • Monitoring for individuals that have gone through a gastric bypass surgery and may not be absorbing enough vitamin D
  • Guidelines for personalized treatment plans while increasing the amount of calcium, vitamin D, magnesium, and/or phosphorus being ingested

When is Vitamin D Testing Ordered?

25-hydroxyvitamin D

When a blood test reveals abnormalities in a person’s calcium levels and/or the person reveals symptoms associated with a vitamin D deficiency. These symptoms can include bone weakness, bone malformation, fractures (osteomalacia). By testing for 25-hydroxyvitamin D, the specialist can determine how significant the deficiency is.

The test can also be requested if additional factors put the patient at risk of a vitamin D deficiency. This can include a person’s age, amount of exposure to the sun, body mass index, fat malabsorption, breastfeeding, skin pigmentation, and recent gastric bypass surgery. An individual in one or more of these categories can be subjected to a test.

This is a necessary test before a treatment can be set up for osteoporosis.

1,25-dihydroxyvitamin D

When an individual is noted for having some form of kidney disease and/or cannot convert 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, this test is administered to determine the cause. In general, this test is not used to determine whether the body has enough calcium. However, it can be used for this purpose. It can also pinpoint the amount of vitamin D in the blood for cases involving lymphoma and sarcoidosis. This has to do with the immune system producing 1,25-dihydroxyvitamin D.

The test may also be administered when vitamin D, phosphorus, calcium, and/or magnesium supplementation is necessary. This can determine how much is needed for the individual’s case.

What do the Test Results Mean?

Vitamin D Testing method is unique in how it is completed and the information it offers. In general, new-age labs will use pre-determined reference intervals during the test. This is done to focus on the lower limit, which looks at the total 25-hydroxyvitamin D in the blood. The upper limit is not tested because toxicity is incredibly rare.

According to the Endocrine Society, a vitamin D deficiency is diagnosed when the 25-hydroxyvitamin D blood level drops below 20 ng/mL (50 nmol/liter).

This also includes a vitamin D insufficiency level of 21-29 ng/ml.

For the U.S. Institute of Medicine, the 25-hydroxyvitamin D level should remain above 20 ng/mL for healthy bone development. It also states that levels beyond 30 ng/mL do not improve a person’s bone health and do not provide enhanced effects. It is important to note, 25-hydroxyvitamin D, and its impact on a person’s overall health varies. In some cases, it is not as clear-cut based on the underlying disorder.

25-hydroxyvitamin D

When there is a lower amount of 25-hydroxyvitamin D in the blood, it can often signal towards inadequate exposure to sunlight and/or reduced vitamin D intake through food sources. It can also signal towards an absorption problem with the person’s intestines. In some cases, certain medications may lead to absorption concerns such as phenytoin (Dilantin).

Studies show that vitamin D deficiency can be associated with certain immune diseases, cancers, and cardiovascular disease.

With a higher amount of 25-hydroxyvitamin D, it may point towards excessive supplementation through food sources or supplements.

1,25-dihydroxyvitamin D

When the amount of 1,25-dihydroxyvitamin D is low, it can lead to health-related issues involving the kidney (i.e., kidney disease). This can often be a sign of early kidney failure in patients.

On the other hand, when the amount of 1,25-dihydroxyvitamin D is high, it means there is too much parathyroid hormone in the blood. This can also mean there is an underlying condition such as lymphoma or sarcoidosis, which can lead to a higher level of 1,25-dihydroxyvitamin D.

When vitamin D and calcium levels are high in the body, they can lead to damaged organs, including the kidney.

When the magnesium levels drop, they can have an added effect on lowering the calcium levels, which impacts parathyroid hormone regulation. This is when it is important to add calcium and magnesium through supplementation.