Side Effects:

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 strict vegetarian or vegan diet and do not consume eggs or dairy products may need vitamin B12 supplements.
• Those 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's disease, may not absorb enough vitamin B12.

Low levels of B12 can cause:

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

See also:

• Megaloblastic anemia
• Pernicious anemia