Hematocrit Test (Hct) -Why am I having this test?

Hematocrit Test test is used to measure the amount of red blood cells (RBCs) in your total blood volume. This test may be done if you have symptoms of anemia, heavy bleeding, or other blood disorders.

This test is often done as part of a complete blood count (CBC) test, which measures several different parts of the blood, including white blood cells (WBCs), RBCs, hematocrit, hemoglobin, and platelets. A CBC may be done as part of routine blood work.

What is being tested?

This test measures the percentage of RBCs in your total blood volume. This percentage is called the hematocrit.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.

Tell a health care provider about:

• All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
• Any blood disorders you have.
• Any surgeries you have had.
• Any medical conditions you have.
• Whether you are pregnant or may be pregnant.

How are the results reported?

Your results will be reported as a percentage or number (volume fraction) that indicates how much of your blood is made up of RBCs. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

• Adult:
  • Male: 42–52% or 0.42–0.52 volume fraction.
  • Non-pregnant female: 37–47% or 0.37–0.47 volume fraction.
  • Pregnant female: greater than 33%.
• Elderly:
  • Male: 38–49% or 0.38–0.49 volume fraction.
  • Female: 34–45% or 0.34–0.45 volume fraction.
• Child or adolescent:
  • Newborn: 44–64%.
  • 2–8 weeks: 39–59%.
  • 2–6 months: 35–50%.
  • 6 months–1 year: 29–43%.
  • 1–6 years: 30–40%.
  • 6–18 years: 32–44%.

What do the results mean?

Results within your reference range are considered normal, meaning that you have a normal amount of red blood cells.

High Hct levels may mean that you have:

• An increased number of red blood cells (erythrocytosis).
• A heart condition present at birth (congenital heart disease).
• An increased number of RBCs being made by the bone marrow (polycythemia vera).
• Severe dehydration.
• Severe COPD (chronic obstructive pulmonary disease).

Low Hct levels may mean that you have:

• A low number of red blood cells (anemia).
• A reduced number and survival of red blood cells (hemoglobinopathy).
• Liver disease (cirrhosis).
• Bleeding.
• A lack (deficiency) of a vitamin or mineral, such as an iron deficiency.
• Bone marrow failure.
• Damage to RBCs due to mechanical heart valves.
• Kidney disease.
• Certain autoimmune diseases, such as rheumatoid arthritis or lupus.
• Certain blood-related cancers, such as lymphoma, multiple myeloma, leukemia, or Hodgkin disease.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

• When will my results be ready?
• How will I get my results?
• What are my treatment options?
• What other tests do I need?
• What are my next steps?

Summary

• The hematocrit (Hct) test is used to measure the amount of red blood cells (RBCs) in your total blood volume. This test is often done as part of a routine complete blood count (CBC) test.
• This test measures the percentage of RBCs in your total blood volume. This percentage is called the hematocrit.
• Talk with your health care provider about what your results mean.