Vitamin B12 is necessary for red blood cell production and for healthy nervous system function. Megaloblastic, or pernicious, anemia occurs because of a rare disorder in which the body cannot absorb enough Vitamin B12, and then produces an inadequate number of red blood cells. Treatment for pernicious anemia often includes B12 injections.
Vitamin B12
Vitamin B12 is normally obtained through animal products in the diet, such as meat, eggs and dairy products. Vegans who do not eat animal products can obtain an adequate amount of B12 through supplements. For this vitamin to be absorbed properly, it must bind to intrinsic factor, a protein released by stomach cells, after which it is absorbed in the small intestine.
The Problem
Some people are born without the ability to make intrinsic factor, and in others, the immune system destroys intrinsic factor. The ability to make intrinsic factor also can be decreased or lost because of gastrointestinal surgery or chronic gastritis. Without sufficient intrinsic factor, the body cannot absorb Vitamin B12, and the person develops pernicious anemia. Symptoms can include fatigue, muscle weakness, decreased appetite, nausea, diarrhea and weight loss. These people need large amounts of Vitamin B12 supplementation. If untreated, the disorder causes progressive nerve damage.
Injections
High levels of Vitamin B12 can be provided through intramuscular injections of cyanocobalamin or hydroxocobalamin. In some countries, injections are prescribed as a monthly treatment, and in others every three months. Some countries also allow the solution to be purchased without a prescription. People typically can perform their own injections at home with syringes commonly used for insulin. Megaloblastic anemia cannot be cured, so these individuals need B12 supplementation for the rest of their lives.
Tablets
B12 injections have traditionally been the preferred treatment for megaloblastic anemia, as physicians had concerns about the effective absorption of oral supplements. However, research has shown that large oral doses can be absorbed even when intrinsic factor is absent, as noted by Merck Manuals Online Medical Library. An increasing number of people with this type of anemia are taking daily B12 tablets in the form of cyanocobalmin at 1000 micrograms instead of injections.
Other Deficiency Causes
Other causes of Vitamin B12 deficiency may require injections on a temporary basis, followed by oral supplements. These include a long-term diet too low in Vitamin B12 which has caused some health problems, chronic alcoholism, Crohn's disease or intestinal malabsorption disorders.
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