Vitamin D 1,25-Dihydroxy Test

The Vitamin D 1,25-Dihydroxy Test test contains 1 test with 3 biomarkers .

Brief Description: The Vitamin D, 1,25-Dihydroxyvitamin test is a laboratory test that measures the level of 1,25-dihydroxyvitamin D in the blood. 1,25-dihydroxyvitamin D is the active form of vitamin D, and this test provides valuable information about the body's overall vitamin D status and its ability to regulate calcium and phosphorus levels.

Also Known As: Calcitriol Test

Testing Method: Chromatography/Mass Spectrometry

Collection Method: Blood Draw 
Specimen: 0.6 mL Serum 

Test Preparation: No preparation required

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

A Vitamin D, 1,25-Dihydroxyvitamin test may be ordered in the following situations:

1. Evaluation of Calcium and Phosphorus Imbalances: When there are abnormalities in blood calcium and phosphorus levels, a Vitamin D, 1,25-Dihydroxyvitamin test may be ordered to assess the underlying cause. Vitamin D plays a crucial role in the regulation of calcium and phosphorus absorption and utilization in the body.

2. Monitoring of Kidney Function: The kidneys play a key role in the production and activation of 1,25-dihydroxyvitamin D. A Vitamin D, 1,25-Dihydroxyvitamin test may be ordered to evaluate kidney function and assess the body's ability to produce active vitamin D.

3. Evaluation of Vitamin D Disorders: This test may be used to evaluate disorders related to vitamin D metabolism, such as vitamin D-dependent rickets, renal osteodystrophy, or other conditions that affect the conversion of vitamin D to its active form.

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:

When a Vitamin D 1,25-Dihydroxy test is ordered, it's typically part of a broader evaluation of bone health, vitamin D status, or related conditions. Here are some tests commonly ordered alongside it:

1. Serum Calcium:

   • Purpose: To measure the level of calcium in the blood.
   • Why Is It Ordered: To assess calcium metabolism and evaluate for conditions like hypercalcemia or hypocalcemia, which can be related to abnormal vitamin D metabolism.

2. Phosphorus:

   • Purpose: To measure the level of phosphorus in the blood.
   • Why Is It Ordered: Phosphorus levels can be affected by vitamin D metabolism and are important in evaluating parathyroid gland function and bone health.

3. Vitamin D 25-Hydroxy (Calcidiol) Test:

   • Purpose: To measure the storage form of vitamin D in the body.
   • Why Is It Ordered: To evaluate overall vitamin D status, which is important for bone health and immune function.

4. Parathyroid Hormone (PTH):

   • Purpose: To measure the level of PTH, which regulates calcium and phosphate levels in the blood.
   • Why Is It Ordered: To assess parathyroid function, as disorders of the parathyroid glands can affect vitamin D metabolism and calcium/phosphorus balance.

5. Kidney Function Test:

   • Purpose: To evaluate kidney function.
   • Why Is It Ordered: The kidneys convert 25-hydroxyvitamin D into its active form, 1,25-dihydroxyvitamin D; thus, kidney function affects vitamin D metabolism.

6. Alkaline Phosphatase (ALP):

   • Purpose: To measure ALP, an enzyme related to bone activity.
   • Why Is It Ordered: Elevated ALP can indicate bone disorders, which may be related to vitamin D metabolism.

7. Magnesium Level:

   • Purpose: To measure the level of magnesium in the blood.
   • Why Is It Ordered: Magnesium is important for vitamin D metabolism, and deficiencies can affect vitamin D function.

These tests, when ordered alongside a Vitamin D 1,25-Dihydroxy test, provide a comprehensive view of an individual’s bone health, vitamin D status, and related metabolic functions. They are critical for diagnosing, managing, and monitoring conditions related to bone metabolism, kidney function, and disorders of calcium regulation. The specific combination of tests will depend on the individual's symptoms, medical history, and initial test results.

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

A Vitamin D, 1,25-Dihydroxyvitamin test may be required in the following conditions or situations:

1. Vitamin D Deficiency or Insufficiency: When there is suspicion of vitamin D deficiency or insufficiency, this test helps determine if there is adequate production and activation of vitamin D in the body.

2. Kidney Disease: Kidney dysfunction can impair the production and activation of vitamin D, leading to low levels of 1,25-dihydroxyvitamin D. The test helps assess kidney function and identify underlying causes of abnormal vitamin D metabolism.

3. Rickets and Osteomalacia: These conditions are characterized by impaired mineralization of bones due to vitamin D deficiency or abnormal metabolism. The Vitamin D, 1,25-Dihydroxyvitamin test helps evaluate the active form of vitamin D and aids in the diagnosis and management of these disorders.

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

Healthcare providers use the results of a Vitamin D, 1,25-Dihydroxyvitamin test in the following ways:

1. Diagnosis of Vitamin D Disorders: Abnormal levels of 1,25-dihydroxyvitamin D can provide diagnostic insights into vitamin D-related disorders, such as vitamin D deficiency, impaired kidney function, or disorders affecting vitamin D metabolism.

2. Management of Vitamin D Therapy: The test helps monitor the response to vitamin D supplementation or other therapeutic interventions. Adjustments to the dosage or type of vitamin D supplementation may be made based on the results.

3. Evaluation of Kidney Function: Abnormal levels of 1,25-dihydroxyvitamin D may indicate underlying kidney dysfunction, and the test helps assess kidney function and guide appropriate management strategies.

4. Assessment of Calcium and Phosphorus Balance: The results of the test, along with calcium and phosphorus levels, aid in evaluating and managing disorders of calcium and phosphorus metabolism, such as hyperparathyroidism or hypoparathyroidism.

It's important to note that the interpretation of Vitamin D, 1,25-Dihydroxyvitamin test results should be done in conjunction with other clinical findings and in consultation with a healthcare provider.

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.

Most Common Questions About the Vitamin D, 1,25-Dihydroxyvitamin test:

Understanding the 1,25-Dihydroxyvitamin D Test

What is the 1,25-Dihydroxyvitamin D test?

The 1,25-Dihydroxyvitamin D test is a blood test that measures the concentration of 1,25-Dihydroxyvitamin D, the active form of vitamin D, in your blood.

What is the role of 1,25-Dihydroxyvitamin D in the body?

1,25-Dihydroxyvitamin D is the active form of Vitamin D. It plays a crucial role in bone health, aiding in the absorption of calcium and phosphorus from the gut. It also plays a role in immune system function and cell growth regulation.

Why is the 1,25-Dihydroxyvitamin D test important?

The 1,25-Dihydroxyvitamin D test is essential in diagnosing and monitoring various health conditions related to bone health, calcium absorption, and parathyroid function. It's often used when other tests suggest an abnormality with these systems.

Understanding 1,25-Dihydroxyvitamin D Test Results

What does a high level of 1,25-Dihydroxyvitamin D mean in the test?

Elevated levels of 1,25-Dihydroxyvitamin D can be seen in conditions like sarcoidosis, some lymphomas, and excessive intake of Vitamin D. It can also be due to high parathyroid hormone levels or kidney disease, as kidneys convert Vitamin D into its active form.

What does a low level of 1,25-Dihydroxyvitamin D mean in the test?

Low levels of 1,25-Dihydroxyvitamin D can be seen in conditions like chronic kidney disease, severe primary hyperparathyroidism, and certain rare inherited disorders. In some cases, low levels can also be due to Vitamin D deficiency.

What is the normal range for 1,25-Dihydroxyvitamin D in the test?

The normal range for 1,25-Dihydroxyvitamin D can vary depending on the patient's age but generally, it falls between 18 to 72 picograms/milliliter (pg/mL).

1,25-Dihydroxyvitamin D Test and Specific Conditions

How is the 1,25-Dihydroxyvitamin D test used in diagnosing sarcoidosis?

In sarcoidosis, granulomas in various body tissues can convert Vitamin D into its active form, leading to elevated levels of 1,25-Dihydroxyvitamin D. This test can assist in diagnosing sarcoidosis when used with other clinical information and test results.

How is the 1,25-Dihydroxyvitamin D test used in diagnosing hyperparathyroidism?

The 1,25-Dihydroxyvitamin D test can be used in conjunction with other tests, like parathyroid hormone (PTH) and calcium, to diagnose hyperparathyroidism. Abnormal Vitamin D levels can suggest a problem with parathyroid function or calcium regulation.

How is the 1,25-Dihydroxyvitamin D test used in assessing kidney function?

The kidneys play a role in the conversion of Vitamin D into its active form, 1,25-Dihydroxyvitamin D. Hence, decreased levels of this Vitamin D metabolite may indicate kidney dysfunction.

Can the 1,25-Dihydroxyvitamin D test be used in the evaluation of rickets or osteomalacia?

Yes, the 1,25-Dihydroxyvitamin D test can be used in the evaluation of metabolic bone diseases like rickets in children or osteomalacia in adults. These conditions can occur due to Vitamin D deficiency or problems with Vitamin D metabolism.

General Queries about the Test

How does the 1,25-Dihydroxyvitamin D test differ from the 25-Hydroxyvitamin D test?

The 25-Hydroxyvitamin D test measures the storage form of Vitamin D and is the most commonly used test to assess Vitamin D status. The 1,25-Dihydroxyvitamin D test, on the other hand, measures the active form of Vitamin D and is typically used when certain diseases are suspected.

Why would a doctor order a 1,25-Dihydroxyvitamin D test instead of a 25-Hydroxyvitamin D test?

A doctor may order a 1,25-Dihydroxyvitamin D test instead of a 25-Hydroxyvitamin D test when certain conditions are suspected, such as sarcoidosis, certain lymphomas, kidney disease, or primary hyperparathyroidism. It can also be ordered when calcium levels are abnormally high or low.

How can certain medications affect the 1,25-Dihydroxyvitamin D test results?

Certain medications can affect the 1,25-Dihydroxyvitamin D test results. These include calcipotriene, used for psoriasis, and some antifungal medications, which can increase levels. Phenobarbital and phenytoin can lower levels, as they increase the metabolism of Vitamin D.

Can Vitamin D supplements affect the 1,25-Dihydroxyvitamin D test results?

Yes, Vitamin D supplements can affect the 1,25-Dihydroxyvitamin D test results. If you take high doses of Vitamin D supplements, it can cause increased levels of 1,25-Dihydroxyvitamin D.

Can I take Vitamin D supplements before the 1,25-Dihydroxyvitamin D test?

Yes, but it's important to inform your healthcare provider about any supplements or medications you are taking, as they can potentially affect the test results.

Understanding the Importance of Vitamin D

How does Vitamin D deficiency affect my health?

Vitamin D deficiency can lead to a host of health issues. In children, it can cause rickets, a disease characterized by bone deformities and growth retardation. In adults, it can lead to osteomalacia, causing bone pain and muscle weakness.

Can the 1,25-Dihydroxyvitamin D test diagnose Vitamin D deficiency?

The 1,25-Dihydroxyvitamin D test isn't typically used to diagnose Vitamin D deficiency. The 25-Hydroxyvitamin D test is the preferred test for that purpose. The 1,25-Dihydroxyvitamin D test is used when certain diseases are suspected.

Why is Vitamin D important for my immune system?

Vitamin D is important for the immune system because it helps to stimulate the production of antimicrobial substances, modulate immune cells, and regulate the immune response.

How does Vitamin D affect bone health?

Vitamin D plays a key role in the body's ability to absorb calcium and phosphorus, two minerals essential for bone health. Deficiency of Vitamin D can lead to a decrease in bone mineral density, leading to conditions like osteoporosis, rickets, or osteomalacia.

How does Vitamin D interact with parathyroid hormone (PTH)?

Vitamin D and parathyroid hormone (PTH) work together to regulate the body's calcium levels. If calcium levels are low, PTH stimulates the kidneys to convert more Vitamin D into its active form, 1,25-Dihydroxyvitamin D, which helps increase calcium absorption from the gut.

Further Inquiries about the Test

Can the 1,25-Dihydroxyvitamin D test help to monitor the effectiveness of Vitamin D supplementation?

Typically, the 25-Hydroxyvitamin D test is used to monitor the effectiveness of Vitamin D supplementation. The 1,25-Dihydroxyvitamin D test is not usually used for this purpose.

How does malnutrition affect the 1,25-Dihydroxyvitamin D test results?

Malnutrition, particularly deficiency in dietary Vitamin D, can affect the 1,25-Dihydroxyvitamin D test results, potentially leading to low levels.

How does sunlight exposure affect the 1,25-Dihydroxyvitamin D test results?

Sunlight exposure helps the skin to produce Vitamin D, which is then converted into its active form, 1,25-Dihydroxyvitamin D, in the kidneys. Hence, adequate sunlight exposure can lead to appropriate levels of 1,25-Dihydroxyvitamin D.

What other tests might be done with the 1,25-Dihydroxyvitamin D test?

The 1,25-Dihydroxyvitamin D test might be done alongside tests for calcium, phosphorus, parathyroid hormone (PTH), and in some cases, the 25-Hydroxyvitamin D test.

Can a 1,25-Dihydroxyvitamin D test be used to monitor treatment in sarcoidosis?

While the 1,25-Dihydroxyvitamin D test isn't typically used as a monitoring tool, in some cases, it may be used to track disease activity or response to treatment in conditions like sarcoidosis, where overproduction of 1,25-Dihydroxyvitamin D may occur.

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