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 other tests are ordered on the same sample, you may need to fast. Your provider will let you know if there are any special instructions.

Blood sample from a vein in the arm using a small needle.

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

Your provider will use your MCV results along with other test results and your medical history to make a diagnosis.

• Red blood cells are smaller than normal: Could be a sign of certain types of anemia (e.g., iron deficiency anemia) or thalassemia (inherited blood disorders that cause fewer healthy red blood cells and less hemoglobin). Limitation: This is just one measurement and must be considered with other results and clinical history. Next step: Talk with your provider to learn what your results mean.
• Red blood cells are larger than normal: Could be a sign of pernicious anemia (possibly from lack of vitamin B12 or diseases that affect B12 use, such as autoimmune diseases, celiac disease, or Crohn's disease), anemia caused by lack of folic acid, or liver disease. Limitation: This is just one measurement and must be considered with other results and clinical history. Next step: Talk with your provider to learn what your results mean.

• 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

Your health care provider will use the results of your MCV, other test results, and your medical history to make a diagnosis.

• 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

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