MCV (Mean Corpuscular Volume)

Why this test may be ordered

• As part of a routine checkup
• If you have a chronic condition that could lead to anemia
• If you have symptoms such as shortness of breath, weakness or fatigue, headache, dizziness, or arrhythmia

Preparation and collection

You don't need any special preparations for an MCV blood 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.

During the 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.

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Understanding results

An MCV test alone cannot diagnose any disease.

• What does low MCV (smaller red blood cells) mean?

  Red blood cells smaller than normal: If your results show that your red blood cells are smaller than normal, it may be a sign of: Certain types of anemia, including iron deficiency anemia, the most common form of anemia. Thalassemia, which is a group of blood disorders that are inherited (passed down through families). Limitation: If your MCV levels are not in the normal range, it doesn't always mean you have a medical problem that needs treatment. Next step: Your provider will use the results of your MCV, other test results, and your medical history to make a diagnosis.
• Red blood cells larger than normal: If your results show that your red blood cells are larger than normal, it may be a sign of: Pernicious anemia, which may be caused by: A lack of vitamin B12 A disease that affects your body's ability to use vitamin B12, such as certain autoimmune diseases, celiac disease, or Crohn's disease Anemia caused by a lack of folic acid Liver disease Limitation: Your age, diet, activity level, medicines, menstrual period, and other conditions can affect the test results. Next step: Your provider will use the results of your MCV, other test results, and your medical history to make a diagnosis.

• An MCV test alone cannot diagnose any disease.
• Not having a normal MCV level does not always mean you have a medical problem that needs treatment.
• Results can be affected by age, diet, activity level, medicines, menstrual period, and other conditions.
• There is a risk of slight pain or bruising at the needle site, though most symptoms go away quickly.

What to do next

Talk with your provider to learn what your results mean.

• An MCV blood test measures the average size of your red blood cells.
• It is often part of a complete blood count (CBC) and is used to check your general health and help diagnose or monitor certain blood disorders, including anemia.
• Your provider may order it as part of a routine checkup, if you have a chronic condition that could lead to anemia, or if you have symptoms such as shortness of breath, weakness, fatigue, headache, dizziness, or arrhythmia.

Evidence source

Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.

U.S. National Library of Medicine: MCV (Mean Corpuscular Volume)

More lab tests A–Z

• Lyme Disease Tests
• Magnesium Blood Test
• Malaria Tests
• Measles and Mumps Tests
• Measuring Blood Pressure
• Meningococcal Disease Tests