MCV (Mean Corpuscular Volume)

What is an MCV Blood Test?

MCV stands for mean corpuscular volume. An MCV blood test measures the average size of your red blood cells.

Red blood cells carry oxygen from your lungs to every cell in your body. Your cells need oxygen to grow, reproduce, and stay healthy. If your red blood cells are too small or too large, it could be a sign of a blood disorder such as anemia, a lack of certain vitamins, or other medical conditions.

Other names: CBC with differential

What is it used for?

An MCV blood test is often part of a complete blood count (CBC). A CBC is a common blood test that measures many parts of your blood, including red blood cells. It is used to check your general health.

An MCV test may also be used with other tests to help diagnose or monitor certain blood disorders, including anemia. There are many types of anemia. An MCV test can help diagnose which type of anemia you have.

Why do I need an MCV blood test?

Your health care provider may order a complete blood count, which includes an MCV test, as part of your regular checkup. You may also have the test if you have a chronic (long-lasting) condition that could lead to anemia or if you have the symptoms of anemia:

• Shortness of breath
• Weakness or fatigue
• Headache
• Dizziness
• Arrhythmia (a problem with the rate or rhythm of your heartbeat)

What happens during an MCV blood 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.

Will I need to do anything to prepare for the test?

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. Your 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 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?

An MCV test alone cannot diagnose any disease. Your provider will use the results of your MCV, other test results, and your medical history to make a diagnosis.

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 type
• Thalassemia, an uncommon genetic condition

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

It's also possible to have anemia with a normal MCV. This may happen if anemia is caused by conditions, such as:

• A sudden loss of blood
• Kidney failure
• Aplastic anemia (uncommon)

If your MCV levels are not in the normal range, it doesn't always mean that you have a medical problem that needs treatment. Diet, activity level, medicines, a menstrual period, and other conditions can affect the test results. Talk with your health care provider to learn what your results mean.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an MCV blood test?

If your provider thinks you may have anemia or another blood disorder, you may have other red blood cell tests with an MCV. These tests may include a red blood cell count and measurements of hemoglobin. All together, these tests are called red blood cell indices.