Hematocrit Test Test
A hematocrit test measures the percentage of your blood that is made up of red blood cells. Red blood cells carry oxygen from your lungs to the rest of your body. Levels that are too high or too low can be a sign of a blood disorder, dehydration, or other medical conditions.
What this test measures
A hematocrit test measures the amount (percent) of your blood that is made up of red blood cells.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
A higher-than-normal hematocrit level may be a sign that your body is making too many red blood cells (possibly due to lung disease, congenital heart disease, heart failure, or polycythemia) or that your blood plasma level is too low (possibly due to dehydration or shock).
Lower-than-normal results
A lower-than-normal hematocrit level may be a sign of blood loss, chronic blood loss, anemia, or conditions causing too many white blood cells (such as bone marrow disease or certain cancers).
Frequently asked questions
What is a hematocrit test?
It is a blood test that measures the percentage of your blood made up of red blood cells.
Why is a hematocrit test done?
It is often part of a complete blood count (CBC) to check general health or help diagnose blood disorders like anemia or polycythemia.
What do the results mean?
Results are a percentage. For example, 42 means 42% of your blood is red blood cells. Normal levels vary by sex, age, smoking, and altitude.
What can cause a high hematocrit?
High hematocrit can be caused by lung disease, congenital heart disease, heart failure, polycythemia, dehydration, or shock.
What can cause a low hematocrit?
Low hematocrit can be caused by blood loss, chronic blood loss, anemia, bone marrow disease, or certain cancers like leukemia.
Related lab tests
Sources
- MedlinePlus: Hematocrit Test — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.