Hematocrit Test
Reviewed
A hematocrit test measures the percentage of your blood that is made up of red blood cells, which carry oxygen from your lungs to the rest of your body. It is often part of a complete blood count (CBC) and is used to check general health or help diagnose blood disorders such as anemia (too few red blood cells) or polycythemia (too many red blood cells).
Preparation and collection
You don't need any special preparations for a hematocrit test. If your provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions to follow.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Normal hematocrit levels vary depending on your sex, age, whether or not you smoke, and the altitude where you live.
- Pregnancy can cause a low hematocrit because your body has more fluid than usual, which decreases the percentage of red blood cells.
- Living at high altitudes with less oxygen in the air may cause a high hematocrit.
- If your results are not in the normal range, it doesn't always mean you have a medical condition that needs treatment.
- Interpretation of results should be done by your healthcare provider.
What to do next
To learn what your test results mean, talk with your provider.