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Vitamin B12 Deficiency Anemia

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Topic Overview

What is vitamin B12 deficiency anemia?


Having vitamin B12 deficiency means that your body does not have enough of this vitamin. You need B12 to make red blood cells camera.gif, which carry oxygen through your body. Not having enough B12 can lead to anemia, which means your body does not have enough red blood cells to do the job. This can make you feel weak and tired. Vitamin B12 deficiency can cause damage to your nerves and can affect memory and thinking.

What causes vitamin B12 deficiency anemia?

Most people get more than enough B12 from eating meat, eggs, milk, and cheese. Normally, the vitamin is absorbed by your digestive system-your stomach and intestines. Vitamin B12 deficiency anemia usually happens when the digestive system is not able to absorb the vitamin. This can happen if:

  • You have pernicious anemia. In this anemia, your body destroys the cells in your stomach that help you absorb vitamin B12.
  • You have had surgery to remove part of the stomach or the last part of your small intestine, called the ileum camera.gif. This includes some types of surgery used to help very overweight people lose weight.
  • You have problems with the way your body digests food, such as sprue (also called celiac disease), Crohn's disease, bacteria growth in the small intestine, or a parasite.

This anemia can also happen if you don't eat enough foods with B12, but this is rare. People who eat a vegan diet and older adults who don't eat a variety of foods may need to take a daily vitamin pill to get enough B12. Other causes include drinking alcohol and taking some prescription and nonprescription medicines.

What is the recommended daily amount of vitamin B12?

The amount of vitamin B12 you need depends on your age.

Daily recommended B12:1
Age (years) Daily amount of B12 (micrograms)
1-30.9 mcg
4-81.2 mcg
9-131.8 mcg
14 and older2.4 mcg
Pregnant women2.6 mcg
Breast-feeding women2.8 mcg

What foods contain B12?

Vitamin B12 is found in foods from animals, such as meat, seafood, milk products, poultry, and eggs. It is not in foods from plants unless it has been added to the food (fortified). Some foods, like cereals, are fortified with vitamin B12.

Supplements containing only B12, or B12 along with other B vitamins and/or folate, are readily available. Also, B12 is usually in multivitamins. Check the label to find out how much B12 is in a supplement.

Estimates of B12 in certain foods2
Food Serving size B12 amount (microgram)
Beef liver3 ounces71 mcg
Clams3 ounces84 mcg
Cereal fortified with 100% daily value for B12 1 serving6 mcg
Rainbow trout3 ounces3 mcg
Nonfat plain yogurt8 ounces1 mcg
Large egg1 egg½ mcg
Chicken breast½ breast½ mcg

WebMD Medical Reference from Healthwise

Last Updated: 2/, 014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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