A hematocrit (he-MAT-uh-krit) test measures the proportion of red blood cells in your blood. Red blood cells carry oxygen throughout your body. Having too few or too many red blood cells can be a sign of certain diseases.
The hematocrit test, also known as a packed-cell volume (PCV) test, is a simple blood test.
A hematocrit test is part of a complete blood count (CBC). Measuring the proportion of red blood cells in your blood can help your doctor make a diagnosis or monitor your response to a treatment.
A lower than normal hematocrit can indicate:
A higher than normal hematocrit can indicate:
The hematocrit is a simple blood test. You won't need to fast before the test or make other preparations.
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. 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 children ages 17 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:
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.