Blood tests 101: Mean corpuscular volume (MCV) test

Mean corpuscular volume (MCV) is a measure of the average size of your red blood cells ( erythrocytes).

MCV, red blood cells, and your thyroid

Having a high MCV might indicate some conditions. An underactive thyroid has a direct effect on red blood cells. MCV is increased by hypothyroidism-making red blood cells larger than normal, thus taking up more volume in your blood (1, 2).

MCV values

Normal MCV values range from 80–100 femtoliters (fl) and vary by age and reference laboratory (3).

What can affect MCV test results?

Anemia, vitamins B9 or B12 or iron deficiency, the menstrual cycle, and activity levels can affect an MCV test read-out.

How we write: our information is based on the results of peer reviewed studies using the National Library of Medicine platform. It is written by scientists and reviewed by external experts. If you believe we might have overseen crucial scientific information, please contact us at

Disclaimer: This information is not intended to mitigate, prevent, treat, cure or diagnose any disease or condition. If you want to change your treatment, lifestyle, your diet, include supplements in your diet or have concerns about your health, please consult your doctor before trying new approaches.


  1. Davidson RJ, et al. A search for the mechanism underlying the altered MCV in thyroid dysfunction: a study of serum and red cell membrane lipids, 1984
  2. Geetha J, et al. Role of red blood cell distribution width (rdw) in thyroid dysfunction, 2012
  3. Aslinia F, et al. Megaloblastic Anemia and Other Causes of Macrocytosis, 2006

Originally published at on July 24, 2020.

Image illustration: Database Center for Life Science (DBCLS). Design: VLM Health



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