A hematocrit test is a blood test that measures the percentage of red blood cells in your blood. Red blood cells are important because they carry oxygen throughout your body. The test is often part of a complete blood count (CBC) and is used to check your general health. It may also be used to help diagnose blood disorders, including anemia, a condition in which you dont have enough red blood cells, and polycythemia, an uncommon disorder in which you have too many red blood cells and your blood becomes too thick.

The hematocrit level is simply the percentage of red cells in your blood. Normal hematocrit levels vary based on age, sex, and race. In adults, normal levels for men range from 41%-50%, while for women, the normal range is slightly lower: 36%-44% . A hematocrit level below the normal range, meaning the person has too few red blood cells, is called anemia. A hematocrit level above the normal range, meaning too many red blood cells, may indicate polycythemia or erythrocytosis.

A hematocrit test is a simple and safe procedure with very few complications. Blood tests to check hematocrit levels are usually done by obtaining blood from a vein, using a needle to fill one or more sample tubes. Other times, providers use a needle prick to obtain a drop of blood. No special preparation such as fasting is required for this test.