A lack of vitamin B12 (B12 deficiency) occurs when the body does not get or is unable to absorb the amount of vitamin that the body needs.

• Many people over age 50 lose the ability to absorb vitamin B12 from foods.
• People who follow a vegetarian or vegan diet should try to eat vitamin B12-fortified foods or talk to their health care provider about taking B12 supplements.
• People who have had gastrointestinal surgery, such as weight loss surgery, lose the ability to absorb vitamin B12.
• People who have digestive disorders, such as celiac disease or Crohn disease, may not absorb enough vitamin B12.

Low levels of B12 can cause:

• Anemia and pernicious anemia
• Loss of balance
• Numbness or tingling in the arms and legs
• Weakness

Supplemental vitamin B12 can be found in the following:

• Almost all multivitamins. Vitamin B12 is better absorbed by the body when it is taken along with other B vitamins, such as niacin, riboflavin, vitamin B6, and magnesium.
• A prescription form of vitamin B12 can be given by injection or as a nasal gel.
• Vitamin B12 is also available in a form that dissolves under the tongue (sublingual).

The Recommended Dietary Allowance (RDA) for vitamins reflects how much of each vitamin most people should receive on a daily basis. The RDA for vitamins may be used as goals for each person.

How much of each vitamin you need depends on your age and gender. Other factors, such as pregnancy and illnesses, are also important. Women who are pregnant or breast-feeding need higher amounts. Ask your provider which amount is best for you.