Vitamin B12 deficiency anemia is a blood problem that occurs when there is not enough of this vitamin in the body. Vitamin B12 helps make red blood cells. Without enough vitamin B12, the body does not produce enough red blood cells, and cells throughout the body do not get the oxygen they need.

Vitamin B12 (also called cobalamin) is found in animal products such as meat, eggs, and milk products. Most people get more than enough of this vitamin from the food they eat. Vitamin B12 deficiency anemia usually occurs when the body cannot absorb this vitamin from food. It can also occur if a person’s diet does not include enough of this vitamin.

A mild deficiency may not cause symptoms. As the anemia becomes worse, symptoms may include weakness, fatigue, diarrhea or constipation, numbness or tingling in the fingers and toes, poor sense of balance, thinking and memory problems, and/or depression. If the condition is not treated right away, symptoms caused by damage to the brain and nerve cells may become permanent.

If vitamin B12 deficiency anemia is suspected, the doctor will do a physical exam, take a medical history, and order blood tests that can help diagnose this condition.

Vitamin B12 deficiency anemia is treated with supplements of vitamin B12. These may be given as shots, pills, or a nasal spray. Vitamin B12 pills contain a higher dose of vitamin B12 than a regular vitamin pill. There is no need for any worry about getting too much vitamin B12, because the body passes extra vitamin B12 out in the urine. Most people need to take supplements for the rest of their lives to keep the condition from coming back.