Vitamin B-12 injections treat pernicious anemia, according to Drugs.com. The injections include cyanocobalamin, a synthetic form of the vitamin. Some patients learn to self-inject vitamin B-12 shots.
Pernicious anemia results from the body's inability to absorb the vitamin B-12 through the digestive tract, according to MedlinePlus. The stomach produces a protein, intrinsic factor, which helps the intestines absorb vitamin B-12 in healthy people. However, atrophic gastritis sometimes weakens the stomach lining so that it no longer produces the protein. Another cause of pernicious anemia is an autoimmune condition that attacks the cells of the stomach lining that produce the protein or intrinsic factor itself.
Although there is a rare hereditary type of pernicious anemia that occurs in babies, it generally affects older adults, reports MedlinePlus. On average, a pernicious anemia patient receives a diagnosis at age 60, and symptoms are rare before age 30.
Some people show no symptoms with the disease. In others, symptoms include pale skin, fatigue, shortness of breath and red, swollen gums. Patients may have a desire to eat nonfood items, such as ice. If vitamin B-12 levels remain low for an extended time, the patient might suffer depression, confusion and a loss of balance. Permanent nerve damage can begin unless the patient receives B-12 supplements within 6 months of developing symptoms, warns MedlinePlus.