Megaloblastic anemia is a form of macrocytic anemia, a blood disorder that happens when your bone marrow produces stem cells that make abnormally large red blood cells. Megaloblastic anemia is a type of vitamin deficiency anemia that happens when you don’t get enough vitamin B12 and/or vitamin B9 (folate). Healthcare providers treat megaloblastic anemia with vitamin B12 and B9 supplements.
Megaloblastic anemia is a form of macrocytic anemia. Macrocytic anemia is a blood disorder that causes your bone marrow to make abnormally large red blood cells. It’s also a type of vitamin deficiency anemia. This condition happens when you don’t get enough vitamin B12 and/or vitamin B9 (folate). Healthcare providers treat megaloblastic anemia with vitamin B12 and vitamin B9 supplements.
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Your body needs a certain amount of healthy red blood cells to carry oxygen from your lungs to your tissues and back again. Like all blood cells, red blood cells start as stem cells in your bone marrow. Vitamin B12 and vitamin B9 help form red blood cells. Without enough vitamin B12 or vitamin B9, your body produces abnormal cells called megaloblasts.
Megaloblasts don’t divide and reproduce like healthy cells, which means there are fewer red blood cells in your bone marrow. The abnormal cells are unusually large, so large they often can’t get out of your bone marrow to move into your bloodstream. And even if they do make their way into your bloodstream, the abnormal cells die earlier than healthy red blood cells. Combined, these factors reduce the number of red blood cells, causing anemia.
Megaloblastic anemia is caused in part by vitamin B12 deficiency. Left untreated, vitamin B12 deficiency can cause neurological issues, including memory loss, problems with balance and paresthesia, which is a sense of tingling or prickling in your arms and legs.
Megaloblastic anemia isn’t rare. Healthcare providers don’t have enough information to say exactly how many people may have megaloblastic anemia.
Megaloblastic anemia happens when you don’t have enough vitamin B12 or vitamin B9 to make sure your bone marrow develops enough healthy red blood cells to carry oxygen throughout your body.
Some people develop vitamin B12 deficiency because their diet doesn’t include enough vitamin B12-rich foods like meat, fish, eggs and dairy products. Some people develop vitamin B12 deficiency because they have conditions or have had medical treatments that affect their ability to absorb vitamin B12. Those conditions include
People may develop vitamin B9 (folate) deficiency if their daily diet doesn’t include green vegetables, fruits, meat and liver or foods that are enriched with folic acid. Other causes may include:
Megaloblastic anemia symptoms are similar to symptoms of other types of anemia:
Vitamin B12 deficiency sometimes affects your nerves, causing symptoms like tingling sensations, loss of sensation or muscle weakness.
Healthcare providers diagnose megaloblastic anemia by doing a physical examination and asking questions about your symptoms. They may do the following blood tests:
Providers treat megaloblastic anemia with vitamin supplements. Here’s more information:
There are several ways to reduce your risk:
Most people recover from megaloblastic anemia after receiving vitamin supplements. Your healthcare provider will monitor your vitamin levels periodically to confirm you’re getting enough vitamin B12 and vitamin B9. For example, they may schedule blood tests a few weeks after you start treatment to confirm the supplements are increasing your vitamin B12 and/or B9 levels.
Take care of yourself by:
A note from Cleveland Clinic
If you have megaloblastic anemia, it means you’re not getting enough vitamin B12 and/or vitamin B9. These vitamins help your body make healthy red blood cells. Healthy red blood cells do essential work. They carry oxygen throughout your body. Fortunately, healthcare providers can treat this vitamin deficiency with supplements to boost your vitamin B12 and vitamin B9 levels. You can support supplements by eating a vitamin-rich diet. Ask your healthcare provider about ways you can make sure you’re getting enough vitamin B12 and vitamin B9. They’ll be glad to help.
Last reviewed by a Cleveland Clinic medical professional on 05/27/2022.
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