Macrocytic Anemia

Overview

What is macrocytic anemia?

Macrocytic anemia is a blood disorder that happens when your bone marrow produces abnormally large red blood cells. These abnormal blood cells lack nutrients red blood cells need to function normally. There are two types of macrocytic anemias. They develop when your body lacks certain nutrients. Macrocytic anemia isn’t a serious illness but it can cause serious medical issues if left untreated.

What are the most common forms of macrocytic anemia?

The two most common forms of macrocytic anemia are megaloblastic macrocytic anemia and non-megaloblastic macrocytic anemia.

  • Megaloblastic macrocytic anemia: This form of macrocytic anemia happens when you don’t get enough vitamin B12 and/or vitamin B6 (folate). Without these nutrients, your bone marrow can’t make healthy red blood cells able to carry oxygen throughout your body. The unhealthy cells also die earlier than normal.
  • Non-megaloblastic macrocytic anemia: This form of macrocytic anemia may happen if you have medical conditions that affect your body’s ability to absorb nutrients.

Medical conditions that cause non-megaloblastic macrocytic anemia

The most common medical conditions are:

  • Myelodysplastic syndrome: This group of disorders happens when something’s gone wrong with your bone marrow and it doesn’t make healthy blood cells.
  • Alcohol use disorder: Drinking excessive amounts of alcohol can keep your body from absorbing vitamin B12.
  • Hypothyroidism: This condition affects your thyroid function and may be linked to macrocytic anemia.

Symptoms and Causes

What causes macrocytic anemia?

People may develop macrocytic anemia when they don’t get enough vitamin B12 and/or folate (vitamin B9) to create healthy red blood cells, or they have medical conditions that prevent their bodies from absorbing those nutrients.

Diagnosis and Tests

How do healthcare providers diagnose macrocytic anemia?

Healthcare providers diagnose macrocytic anemia by doing a physical examination and asking questions about your symptoms. They may also perform the following blood tests:

  • Complete blood count (CBC): Healthcare providers use this test to evaluate your red blood cell count and function.
  • Peripheral blood smear (PBS): This test is a technique healthcare providers use to examine your blood cells. Unlike some blood tests that are analyzed by a machine, healthcare providers analyze your blood cells by looking at them under a microscope.
  • Reticulocyte count: A reticulocyte count measures the number of immature red blood cells (reticulocytes) in your bone marrow. Healthcare providers measure reticulocytes to determine if your bone marrow is producing enough healthy red blood cells.

Management and Treatment

How do healthcare providers treat macrocytic anemia?

Healthcare providers evaluate the condition’s underlying cause to develop treatment so your bone marrow can create healthy red blood cells. For example, you may have macrocytic anemia because you’re not eating enough food or your diet lacks important nutrients such as vitamin B12 or folate (vitamin B9). Sometimes, people are eating well, but there’s something keeping their bodies from absorbing nutrients. If that’s your situation, your healthcare provider may prescribe supplements. They may recommend you take supplements until blood tests show your bone marrow is developing healthy red blood cells.

If you have macrocytic anemia because you have an underlying condition, your healthcare provider will treat the underlying condition. For example, some people have conditions that keep their bodies from absorbing essential nutrients.

Many people develop macrocytic anemia because they drink a lot of alcohol. In that case, your healthcare provider may prescribe medical treatment and recommend treatment to help you manage your alcohol intake.

Prevention

How can I prevent macrocytic anemia?

Macrocytic anemia happens for several reasons, including underlying illness that you may not be able to prevent. If you don’t have an underlying illness, however, there are steps you can take to reduce your risk and possibly prevent macrocytic anemia, such as:

  • Pay attention to your overall health. Macrocytic anemia symptoms start out mild and grow worse over time. If you notice changes in your body, like feeling extremely tired, talk to your healthcare provider.
  • Eat a healthy diet. Most of the time, not getting enough vitamin B12 and/or folate (vitamin B9) increases your risk for macrocytic anemia.

Outlook / Prognosis

What can I expect if I have macrocytic anemia?

Most people recover from macrocytic anemia after receiving vitamin supplements. Prognosis, or expected outcome, for people who have underlying conditions depends on the underlying condition and their situation.

Living With

How do I take care of myself?

Take care of yourself by:

  • Take supplements your healthcare provider prescribed.
  • Develop healthy eating habits that ensure you’re getting enough vitamin B12 and folate (vitamin B9).
  • Follow up with your healthcare provider if you notice your anemia symptoms return.

A note from Cleveland Clinic

People develop macrocytic anemia when they don’t get enough nutrients to help their bodies develop healthy red blood cells. Macrocytic anemia can happen if people follow certain diets or have certain underlying conditions. Macrocytic anemia isn’t a serious illness but it can cause serious medical issues. You may be able to prevent macrocytic anemia by eating well. If you’re concerned about macrocytic anemia, ask your healthcare provider for help. They’ll assess your situation and recommend ways you can improve your diet. If you have macrocytic anemia, your healthcare provider will prescribe supplements to replace missing nutrients. They’ll also help you develop habits to keep you healthy.

Last reviewed by a Cleveland Clinic medical professional on 05/16/2022.

References

  • Hariz A, Bhattacharya PT. Megaloblastic Anemia. (https://www.ncbi.nlm.nih.gov/books/NBK537254/?msclkid=44e7ceccc17511eca3bf5b09574b20dc) [Updated 2021 Oct 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Accessed 5/16/2022.
  • Nagao T, Hirokawa M. Diagnosis and Treatment of Macrocytic Anemias n Adults. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5689413/) J Gen Fam Med. 2017;18(5):200-204. Published 2017 Apr 13. Accessed 5/16/2022.
  • Merck Manuals. Megaloblastic Macrocytic Anemia. (https://www.merckmanuals.com/professional/hematology-and-oncology/anemias-caused-by-deficient-erythropoiesis/megaloblastic-macrocytic-anemias) Accessed 5/16/2022.
  • Moore CA, Adil A. Macrocytic Anemia. (https://www.ncbi.nlm.nih.gov/books/NBK459295/) [Updated 2021 Jul 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Accessed 5/16/2022.

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