A hematocrit (he-MAT-uh-krit) test measures the proportion of red blood cells in the blood. Red blood cells carry oxygen throughout the body. Having too few or too many of them can be a sign of certain diseases.

The hematocrit test is a simple blood test. It is sometimes referred to as a packed-cell volume test.

Why it's done

A hematocrit test can help your health care team make a diagnosis or monitor how you respond to a treatment. The test is done as part of a complete blood count (CBC).

When the hematocrit value is low, the proportion of red blood cells in the blood is lower than usual. This can indicate:

  • The blood has too few healthy red blood cells. This condition is called anemia.
  • That the body does not have enough vitamins or minerals.
  • Recent or long-term blood loss.

When the hematocrit value is high, the proportion of red blood cells in the blood is higher than normal. This can indicate:

  • Dehydration.
  • A disorder that causes your body to produce too many red blood cells, such as polycythemia vera.
  • Lung or heart disease.
  • Living at a high altitude, such as on a mountain.

More Information

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.

How you prepare

The hematocrit is a simple blood test. You won't need to fast before the test or make other preparations.

What you can expect

The blood sample is generally drawn with a needle from a vein in your arm. You may feel some tenderness at the site, but you'll be able to resume normal activities afterward.


Results from your hematocrit test are reported as the percentage of blood cells that are red blood cells. Typical ranges vary substantially with race, age and sex. The definition of typical red-blood cell percentage also may vary somewhat from one medical practice to another. This is because laboratories decide what is a healthy range based on the population in their area.

Generally, a typical range is considered to be:

  • For men, 38.3% to 48.6%.
  • For women, 35.5% to 44.9%.

For children ages 15 and younger, the typical range varies by age and sex.

Your hematocrit test provides just one piece of information about your health. Talk to your health care team about what your hematocrit test result means.

Accuracy of test results

A number of factors can affect the outcome of a hematocrit test. There are some situations when hematocrit is not in the typical range but it does not mean a person is sick. These include:

  • Living at a high altitude increases hematocrit.
  • Pregnancy lowers hematocrit.
  • Recent loss of a lot of blood lowers hematocrit.
  • Recent blood transfusion may raise hematocrit.
  • Severe dehydration may raise hematocrit.

Your health care team will consider possible complicating factors when interpreting the results of your hematocrit test. If results provide conflicting or unexpected information, they may want to repeat the hematocrit test and do other blood tests.

Sept. 19, 2023
  1. Powers JM, et al. Approach to the child with anemia. https://www.uptodate.com/contents/search. Accessed April 29, 2023.
  2. Mean RT, et al. Diagnostic approach to anemia in adults. https://www.uptodate.com/contents/search. Accessed April 29, 2023.
  3. Types of blood tests. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health/blood-tests. Accessed April 29, 2023.
  4. Tefferi A. Diagnostic approach to the patient with erythrocytosis/polycythemia. https://www.uptodate.com/contents/search. Accessed April 29, 2023.
  5. Hoffman R, et al. The polycythemias. In: Hematology: Basic Principles and Practice. 8th ed. Elsevier; 2023. https://www.clinicalkey.com. Accessed April 29, 2023.
  6. Complete blood cell count (CBC) with differential, blood. Mayo Medical Laboratories. https://www.mayocliniclabs.com/test-catalog/overview/9109#. Accessed April 28, 2023.
  7. Complete blood cell count (CBC). American Academy of Family Physicians. https://familydoctor.org/complete-blood-count-cbc/. Accessed April 30, 2023.
  8. Pruthi RK (expert opinion). Mayo Clinic. May 1, 2023.

Hematocrit test