Hematocrit (HCT)

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Also known as: Crit, HCT, Hematocrit HCT, Packed cell volume, PCV


Hematocrit is a blood test that measures the percentage of the volume of whole blood that is made up of red blood cells. This measurement depends on the number of red blood cells and the size of red blood cells.
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The Hematocrit (HCT) test contains 1 test with 1 biomarker.

Brief Description: The hematocrit test, also known as the Hct test, measures the proportion of red blood cells (RBCs) in relation to the total volume of blood. It is a fundamental component of a complete blood count (CBC) and provides essential information about an individual's blood composition.

Also Known As: HCT Test, Crit Test, Packed Cell Volume Test, PCV Test

Collection Method: Blood Draw

Specimen Type: Whole Blood

Test Preparation: No preparation required

When is a Hematocrit test ordered?

A full blood count usually includes a hematocrit measurement. It can also be ordered as part of a general health assessment, either by itself or in conjunction with a hemoglobin level. When a person develops signs and symptoms of a disorder that affects RBCs, such as anemia or polycythemia, these tests are frequently done.

When someone has signs and symptoms of severe dehydration, such as intense thirst, dry mouth or mucous membranes, and a lack of perspiration or urination, a hematocrit may be requested.

When someone has been identified with recurrent bleeding difficulties, anemia, or polycythemia, this test may be repeated numerous times or on a regular basis to check the success of treatment. It may also be ordered on a regular basis for persons receiving therapy for cancers that affect the bone marrow.

What does a Hematocrit blood test check for?

A hematocrit is a test that determines the percentage of red blood cells in a person’s blood. RBCs, white blood cells, and platelets are suspended in plasma, a fluid component of blood. The hematocrit is a ratio that compares the volume of red blood cells to the volume of all of these components together, which is known as whole blood. A percentage or fraction is used to express the value. A hematocrit of 40%, for example, indicates that there are 40 milliliters of red blood cells per 100 milliliters of blood.

The hematocrit is a quick and easy approach to assess a person’s red blood cells and screen for disorders like anemia. It’s frequently done in conjunction with a hemoglobin level, and it’s also a part of a complete blood count, which is commonly used to assess a person’s overall health.

RBCs are made in the bone marrow and discharged into the bloodstream when they are fully mature or almost so. They normally constitute about 37 to 49 percent of the blood volume. Hemoglobin, a protein that binds to oxygen, is found in RBCs. RBCs’ main job is to transport oxygen from the lungs to the body’s tissues and organs. They also transfer a little amount of carbon dioxide from tissues and organs back to the lungs, where it is exhaled.

RBCs have a 120-day lifespan, and the bone marrow must constantly manufacture new RBCs to replace those that have aged and degraded or have been lost due to hemorrhage. A variety of disorders can impact the bone marrow’s ability to produce new RBCs or the longevity of those already in circulation, as well as cause substantial bleeding.

The hematocrit measures both the number and volume of red blood cells. The hematocrit will drop when the size of the RBCs decreases, and vice versa. In general, the hematocrit will rise as the number of red blood cells increases, and it will fall to less than normal when the number of RBCs produced by the bone marrow decreases, the number of RBCs destroyed increases, or blood is lost due to hemorrhage. The overall amount of RBCs and hematocrit will diminish if the bone marrow is unable to manufacture new RBCs quickly enough, resulting in anemia.

Anemia is a condition in which the body is unable to provide adequate oxygen to tissues and organs, resulting in weariness and weakness. Too many RBCs are created in polycythemia, and the blood thickens, causing sluggish blood flow and other complications.

Lab tests often ordered with a Hematocrit test:

When a Hematocrit test is ordered, it's often part of a broader evaluation of blood health. Here are some tests commonly ordered alongside it:

  1. Complete Blood Count (CBC):

    • Purpose: To provide a comprehensive evaluation of the blood, including red and white blood cells, and platelets.
    • Why Is It Ordered: The CBC gives detailed information about the various cellular components of blood, including hemoglobin levels, red blood cell count, and size, which are important for interpreting the hematocrit value.
  2. Hemoglobin Test:

    • Purpose: To measure the amount of hemoglobin, the oxygen-carrying protein in red blood cells.
    • Why Is It Ordered: Hemoglobin levels correlate with hematocrit values and are crucial for diagnosing anemia and other blood disorders.
  3. Red Blood Cell Indices (MCV, MCH, MCHC, RDW):

    • Purpose: To measure the size (MCV), hemoglobin amount per cell (MCH), concentration of hemoglobin in each cell (MCHC), and red cell distribution width (RDW).
    • Why Is It Ordered: These indices help in characterizing the type of anemia or other red blood cell disorders.
  4. Iron Studies:

    • Purpose: To evaluate iron status.
    • Why Is It Ordered: To assess for iron deficiency or overload, common causes of anemia and abnormal hematocrit levels.
  5. Vitamin B12 and Folate Levels:

    • Purpose: To measure levels of these essential vitamins.
    • Why Is It Ordered: Deficiencies in vitamin B12 and folate can lead to anemia, affecting hematocrit values.
  6. Reticulocyte Count:

    • Purpose: To measure the number of young red blood cells (reticulocytes) in the blood.
    • Why Is It Ordered: To evaluate bone marrow function and the body’s response to anemia.
  7. Erythropoietin Level:

    • Purpose: To measure the level of erythropoietin, a hormone that stimulates red blood cell production.
    • Why Is It Ordered: To help understand the cause of certain types of anemia or polycythemia.
  8. Kidney Function Test:

    • Purpose: To evaluate kidney function.
    • Why Is It Ordered: The kidneys produce erythropoietin, so kidney function can impact red blood cell production and hematocrit levels.

These tests, when ordered alongside a Hematocrit test, provide a comprehensive assessment of blood health and help diagnose the cause of abnormalities in red blood cell quantity and quality. They are crucial for diagnosing and managing conditions such as anemia, polycythemia, and other hematological disorders. The specific combination of tests will depend on the individual’s symptoms, medical history, and initial test results.

Conditions where a Hematocrit test is recommended:

A hematocrit test is useful for diagnosing and monitoring various conditions, including:

  • Anemia: Low hematocrit levels can indicate different types of anemia, such as iron-deficiency anemia, vitamin B12 deficiency anemia, and hemolytic anemia.
  • Polycythemia: High hematocrit levels may indicate polycythemia, a condition where there's an excess of red blood cells in the blood.

How does my health care provider use a Hematocrit test?

The hematocrit test is frequently used to diagnose anemia, usually in conjunction with a hemoglobin test or as part of a full blood count. The test can be used to detect, diagnose, or track a variety of illnesses and disorders that impact the amount of red blood cells in the blood. RBCs are red blood cells that circulate in the blood and transport oxygen throughout the body.

Some circumstances influence RBC formation in the bone marrow, resulting in an increase or decrease in the number of mature RBCs discharged into circulation. The longevity of RBCs in the circulation may be affected by other factors. The overall number of RBCs and hematocrit will diminish if there is increased destruction or loss of RBCs, and/or the bone marrow is unable to make new ones quickly enough, leading in anemia.

The hematocrit can tell if there's a problem with RBCs, but it can't tell what's causing it. A blood smear, reticulocyte count, iron studies, vitamin B levels, and, in more severe cases, a bone marrow examination are some of the other tests that may be conducted at the same time or as follow-up to establish a reason.

What do my Hematocrit test results mean?

Red blood cells make up between 37 percent to 49 percent of the total amount of blood.

Because a hematocrit is frequently performed as part of a complete blood count, other components including RBC count, hemoglobin, reticulocyte count, and/or red blood cell indices are taken into account. Other considerations include age, gender, and race. In general, the hematocrit reflects the RBC count and hemoglobin readings.

Anemia is diagnosed by a low hematocrit, low RBC count, and low hemoglobin.

Most Common Questions About the Hematocrit test:

Understanding the Hematocrit Test

What is the Hematocrit test, and why is it performed?

The Hematocrit test measures the proportion of red blood cells to the total volume of blood. It's performed to evaluate anemia, polycythemia (high red blood cell count), and hydration status, and to monitor treatments for various blood disorders.

What conditions can the Hematocrit test help diagnose?

The Hematocrit test can help diagnose anemia, polycythemia, dehydration, malnutrition, and chronic diseases that affect red blood cell production. It's a valuable tool in understanding the underlying causes of symptoms like fatigue or weakness.

Interpretation of Hematocrit Test Results

What do the results of the Hematocrit test mean?

Results of the Hematocrit test are expressed as a percentage. Normal ranges vary by age, sex, and health conditions. Low hematocrit may indicate anemia, while high hematocrit may suggest dehydration or polycythemia.

How can other medical conditions affect the Hematocrit test results?

Other medical conditions, such as chronic kidney disease, lung diseases, or heart failure, can influence Hematocrit levels by affecting red blood cell production or plasma volume.

How are Hematocrit test results used in conjunction with other blood tests?

The Hematocrit test is often part of a complete blood count (CBC), and the results are interpreted alongside other measurements, such as hemoglobin, red blood cell count, and mean corpuscular volume (MCV), to provide a comprehensive picture of blood health.

Clinical Applications of the Hematocrit Test

How is the Hematocrit test used in the treatment of anemia?

The Hematocrit test helps diagnose anemia and identify its underlying cause (e.g., iron deficiency, chronic disease). By monitoring Hematocrit levels, healthcare providers can assess the effectiveness of treatments like iron supplements or blood transfusions.

Can the Hematocrit test be used to monitor hydration status?

Yes, the Hematocrit test can be used to monitor hydration status. Elevated Hematocrit levels may indicate dehydration, as the reduced plasma volume concentrates the red blood cells.

How is the Hematocrit test used in the management of chronic kidney disease?

Chronic kidney disease can affect red blood cell production, leading to anemia. The Hematocrit test is used to monitor this condition and guide treatments such as erythropoiesis-stimulating agents (ESAs) or iron therapy.

Methodological Considerations of the Hematocrit Test

Can medications or lifestyle factors interfere with Hematocrit test results?

Certain medications, such as chemotherapy drugs, and lifestyle factors like smoking or high altitude, can affect Hematocrit levels and may need to be considered when interpreting test results.

How specific is the Hematocrit test for diagnosing underlying conditions?

While the Hematocrit test can indicate abnormalities in red blood cell volume, it is not specific to a particular underlying condition. Further tests and clinical evaluation are typically required for an accurate diagnosis.

Hematocrit Test in Special Populations

Is the Hematocrit test used in critical care settings?

In critical care settings, the Hematocrit test can provide rapid insights into conditions like hemorrhage, fluid overload, or sepsis, guiding urgent medical interventions.

How is the Hematocrit test utilized in sports medicine?

The Hematocrit test is used in sports medicine to assess hydration status and detect potential blood doping, a practice where athletes illegally boost their red blood cell count to enhance performance.

What are the implications of abnormal Hematocrit levels in cancer patients?

Abnormal Hematocrit levels in cancer patients may reflect anemia caused by the disease itself or treatment effects. It may influence treatment decisions and overall prognosis.

How is the Hematocrit test used to monitor therapeutic blood removal procedures?

In conditions like polycythemia vera, therapeutic blood removal may be necessary. The Hematocrit test helps guide these procedures and monitor their effectiveness.

Can the Hematocrit test be used to evaluate nutritional status?

Yes, the Hematocrit test can help evaluate nutritional status, especially related to deficiencies in iron, vitamin B12, or folate, which can lead to anemia.

How is the Hematocrit test used in the evaluation of blood disorders like thalassemia?

In blood disorders like thalassemia, the Hematocrit test contributes to diagnosis and monitoring, often in conjunction with other specialized tests.

Can the Hematocrit test help in evaluating the risk of cardiovascular diseases?

Elevated Hematocrit levels may be associated with increased viscosity of the blood and potential risks for clotting or cardiovascular diseases. It can be a component of risk assessment.

How is the Hematocrit test used in the management of patients undergoing surgery?

Preoperative Hematocrit testing helps assess potential risks, such as anemia or blood clotting disorders, that could affect surgical outcomes. Postoperative monitoring may detect hemorrhage or other complications.

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

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