What causes enlarged red blood cells (macrocytosis)?
Answer From Rajiv K. Pruthi, M.B.B.S.
Macrocytosis is a term used to describe red blood cells that are larger than normal. Also known as megalocytosis or macrocythemia, this condition typically causes no signs or symptoms and is usually detected incidentally on routine blood tests.
Macrocytosis isn't a specific disease, but it may indicate an underlying problem that requires medical evaluation. Common causes of macrocytosis include:
- Vitamin B-12 deficiency
- Folate deficiency
- Liver disease
- A side effect of certain medications, such as those used to treat cancer, seizures and autoimmune disorders
- Increased red blood cell production by the bone marrow to correct anemia, for example, after blood loss
- An underlying bone marrow cancer called myelodysplastic syndrome
If you have macrocytosis, blood tests can help determine its cause. In some cases, it may be necessary to remove a sample of your bone marrow — the spongy tissue inside your bones — for testing.
Management of macrocytosis consists of finding and treating the underlying cause. In the case of vitamin B-12 or folate deficiency, treatment may include diet modification and dietary supplements or injections. If the underlying cause is resulting in severe anemia, you might need a blood transfusion.
Rajiv K. Pruthi, M.B.B.S.
May 06, 2021
From Mayo Clinic to your inbox
Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on managing health.
ErrorEmail field is required
ErrorInclude a valid email address
To provide you with the most relevant and helpful information, and understand which
information is beneficial, we may combine your email and website usage information with
other information we have about you. If you are a Mayo Clinic patient, this could
include protected health information. If we combine this information with your protected
health information, we will treat all of that information as protected health
information and will only use or disclose that information as set forth in our notice of
privacy practices. You may opt-out of email communications at any time by clicking on
the unsubscribe link in the e-mail.
Thank you for subscribing!
You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox.
Sorry something went wrong with your subscription
Please, try again in a couple of minutes
See more Expert Answers
- Kaferle J, et al. Evaluation of macrocytosis. American Family Physician. 2009;79:203.
- Schrier SL. Macrocytosis/macrocytic anemia. http://www.uptodate.com/home. Accessed April 17, 2019.
- Pruthi RK (expert opinion). Mayo Clinic, Rochester, Minn. April 17, 2019.