Hematocrit Test

By Medically reviewed by hellodoktor


What is Hematocrit Test?

Hematocrit is the percentage of red blood cells in the total blood volume. Red blood cells are vital to your health. Imagine them as the subway system of your blood. They transport oxygen and nutrients to various locations in your body. For you to stay healthy, your body needs to have the correct proportion of red blood cells.

Your doctor may order a hematocrit, or Hct, test if they think you have too few or too many red blood cells.

Why is Hematocrit Test performed?

A hematocrit test can help your doctor diagnose you with a particular condition, or it can help them determine how well your body is responding to a certain treatment. The test can be ordered for a variety of reasons, but it’s most often used to test for:

If your doctor orders a complete blood count (CBC) test, the hematocrit test is included. Other tests in a CBC are a hemoglobin and reticulocyte count. Your doctor will look at your overall blood test results to gain an understanding of your red blood cell count.


What should I know before receiving Hematocrit Test?

A hematocrit test is not associated with any major side effects or risks. You may have some bleeding or throbbing at the site where the blood is drawn. Let your doctor know if you experience any swelling or bleeding that doesn’t stop within a few minutes of pressure being applied to the puncture site.


How to prepare for Hematocrit Test?

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

What happens during Hematocrit Test?

A medical provider will need a small sample of blood to test your hematocrit. This blood can be drawn from a finger prick or taken from a vein in your arm.

If the hematocrit test is part of a CBC, a lab technician will draw blood from a vein, typically from the inside of your elbow or from the back of your hand. The technician will clean the surface of your skin with an antiseptic and place an elastic band, or tourniquet, around your upper arm to help the vein swell with blood.

They’ll then insert a needle in the vein and collect a blood sample in one or more vials. The technician will remove the elastic band and cover the area with a bandage to stop the bleeding. A blood test can be slightly uncomfortable. When the needle punctures your skin, you might feel a prick or pinching sensation. Some people also feel faint or lightheaded when they see blood. You may experience minor bruising, but this will clear up within a few days. The test will take only a few minutes, and you can resume everyday activities after it’s finished. Your sample will be sent to a lab for analysis.

What happens after Hematocrit Test?

In the laboratory, your hematocrit is evaluated using a centrifuge, which is a machine that spins at a high rate to cause the contents of your blood to separate. A lab specialist will add a special anticoagulant to keep your blood from clotting.

When the test tube is taken out of the centrifuge, it will have settled into three parts:

  • Red blood cells
  • Anticoagulant
  • Plasma, or the fluid in your blood

Each component will settle in a different part of the tube, with the red blood cells moving to the bottom of the tube. The red blood cells are then compared to a guide that tells what proportion of your blood they make up.

If you have any questions about the Hematocrit Test, please consult with your doctor to better understand your instructions.

Explanation of results

What do my results mean?

Results from your hematocrit test are reported as the percentage of blood cells that are red blood cells. Normal ranges vary substantially with race, age and sex. The definition of normal red-blood cell percentage also varies from one medical practice to another.

Generally, a normal range is considered to be:

  • For men, 38.8 to 50 percent
  • For women, 34.9 to 44.5 percent
  • For children ages 15 and younger, the normal range varies by age and sex.

Your hematocrit test provides just one piece of information about your health. Talk to your doctor about what your hematocrit test result means in light of the symptoms you’re experiencing and the results of other diagnostic tests.

A number of factors can affect the outcome of a hematocrit test and yield inaccurate or misleading results, including:

  • Living at a high altitude
  • Pregnancy
  • Significant recent blood loss
  • Recent blood transfusion
  • Severe dehydration

Your doctor will take into account possible complicating factors when interpreting the results of your hematocrit test. Your doctor may want to repeat the hematocrit test and do other blood tests if results provide conflicting or unexpected information.

Depending on the laboratory and hospital, the normal range for Hematocrit Test may vary. Please discuss with your doctor any questions you may have about your test results.


Hello Health Group does not provide medical advice, diagnosis or treatment.


Review Date: November 4, 2018 | Last Modified: September 12, 2019

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