Megaloblastic Anemia

Megaloblastic anemia is a blood disorder that happens when your bone marrow makes abnormally large red blood cells. You may develop megaloblastic anemia if you have low levels of vitamin B12 or vitamin B9 (folate), or take certain medications.

Vitamins B12 and B9 help form red blood cells. Your body makes abnormal cells called megaloblasts when you don’t have enough vitamin B12 or vitamin B9. The abnormal cells lead to anemia because they:

• Don’t divide like healthy cells, so you have fewer red blood cells in your bone marrow
• Are very large, so they can’t move from your bone marrow to your bloodstream
• Die earlier than healthy red blood cells

Healthcare providers treat megaloblastic anemia with vitamin B12 and vitamin B9 supplements.

Symptoms of megaloblastic anemia

This disease may cause:

• Fatigue
• Lightheadedness
• Shortness of breath
• Skin that’s paler than usual
• Weakness

Megaloblastic anemia causes

This disease happens when you don’t have enough vitamin B12 or vitamin B9. These vitamins help your bone marrow make healthy red blood cells. The blood cells carry oxygen throughout your body. Some medications can cause megaloblastic anemia, as well.

You may have vitamin B12 deficiency if you don’t get enough of this nutrient from the foods you eat. Certain inherited disorders, digestive diseases or pernicious anemia may lead to low vitamin B12 levels.

Folate deficiency is when your body doesn’t get enough vitamin B9. Some digestive diseases, health conditions (like anemia) or medical treatments may cause it.

How doctors diagnose megaloblastic anemia

Your healthcare provider will ask about your symptoms and do a physical exam. They may request blood tests, which involve a provider taking small samples of your blood. The tests may include:

• Complete blood count (CBC) to check the size of your red blood cells
• Methylmalonic acid test to check for low levels of vitamin B12
• Peripheral blood smear to look for large red blood cells
• Red blood cell distribution width (RDW) test to look for variations in the size of your red blood cells
• Reticulocyte count to see if your bone marrow is making enough new red blood cells

How do healthcare providers treat megaloblastic anemia?

Vitamin supplements are the most common treatment. Your treatment will depend on the specific vitamin deficiency you have:

• Vitamin B12 deficiency treatment: You may have a series of vitamin B12 shots over several weeks. The supplements will boost your vitamin B12 levels. Some people may need these shots for the rest of their lives. That’s the case for people who can’t absorb the vitamin or who have pernicious anemia.
• Vitamin B9 deficiency treatment: Your provider may prescribe folic acid tablets to manage this deficiency. Sometimes, supplements improve megaloblastic anemia symptoms and hide an underlying vitamin B12 deficiency. Your provider will check your vitamin B12 levels to be sure they’re normal.

What can I expect if I have megaloblastic anemia?

Most people recover once they take vitamin supplements. Your healthcare provider may schedule follow-up blood tests. The tests will show if your vitamin levels have increased as they should.

What’s the difference between anemia and megaloblastic anemia?

Anemia is when you have low levels of red blood cells. Megaloblastic anemia is a specific type of anemia. It happens when your red blood cells are larger than usual.

Can I reduce my risk of developing megaloblastic anemia?

Several factors may cause this disease. While you can’t prevent all of them, the following steps may reduce your risk:

• Plan your meals so you get plenty of vitamin B12-rich foods and folate.
• Drink alcohol only in moderation. Regular alcohol consumption may affect your digestive system and keep your body from absorbing vitamin B12.
• Work with your healthcare provider to manage any conditions that keep your body from absorbing vitamin B12.