What is a hematocrit test?
A hematocrit test is a type of blood test. Your blood is made up of red blood cells, white blood cells, and platelets. These cells and platelets are suspended in a liquid called plasma. A hematocrit test measures how much of your blood is made up of red blood cells. Red blood cells contain a protein called hemoglobin that carries oxygen from your lungs to the rest of your body. Hematocrit levels that are too high or too low can indicate a blood disorder, dehydration, or other medical conditions.
Other names: HCT, packed cell volume, PCV, Crit; Packed Cell Volume, PCV; H and H (Hemoglobin and Hematocrit)
What is it used for?
A hematocrit test is often part of a complete blood count (CBC), a routine test that measures different components of your blood. The test is also used to help diagnose blood disorders such as anemia, a condition in which your blood doesn’t have enough red cells, or polycythemia vera, a rare disorder in which your blood has too many red cells.
Why do I need a hematocrit test?
Your health care provider may have ordered a hematocrit test as part of your regular checkup or if you have symptoms of a red blood cell disorder, such as anemia or polycythemia vera. These include:
Symptoms of anemia:
- Shortness of breath
- Weakness or fatigue
- Cold hands and feet
- Pale skin
- Chest pain
Symptoms of polycythemia vera:
- Blurred or double vision
- Shortness of breath
- Flushed skin
- Excessive sweating
What happens during a hematocrit test?
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for a hematocrit test. If your health care 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 health care provider will let you know if there are any special instructions to follow.
Are there any risks to the test?
There is very little risk to having a hematocrit test or other type of blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
If test results show your hematocrit levels are too low, it may indicate:
- Nutritional deficiency of iron, vitamin B-12, or folate
- Kidney disease
- A bone marrow disease
- Certain cancers such as leukemia, lymphoma, or multiple myeloma
If test results show your hematocrit levels are too high, it may indicate:
- Dehydration, the most common cause of high hematocrit levels. Drinking more fluids will usually bring your levels back to normal.
- Lung disease
- Congenital heart disease
- Polycythemia vera
If your results are not in the normal range, it doesn’t necessarily mean that you have a medical condition requiring treatment. To learn more about your results, talk to your health care provider.
Is there anything else I need to know about a hematocrit test?
Many factors can affect your hematocrit levels, including a recent blood transfusion, pregnancy, or living at a high altitude.