Vitamin B-12 is generally the only B vitamin available by injection outside of a medical setting. As an injection, it is available as the synthetic form called cyanocobalamin. Vitamin B-12 injections are beneficial for certain health conditions, and some people take them for an energy boost and a weight loss aid. Vitamin B-12 injections are generally safe, but may potentially interfere with the effectiveness of certain medications, according to Drugs.com. You may experience mild side effects such as nausea, headache, weakness and rash. For serious side effects -- trouble breathing, swelling and chest pain -- seek emergency attention. Consult a qualified health care provider before beginning vitamin B injections.
B-12 Deficiency Anemia
Vitamin B-12 is necessary for red blood cell production. Insufficient levels of vitamin B-12 can lead to anemia, which is a low red blood cell count, explains the Office of Dietary Supplements. This type of anemia involves abnormally large red blood cells, a condition called megaloblastic anemia. Symptoms include fatigue, weakness, lack of appetite, weight loss and constipation.
Pernicious anemia, a specific type of megaloblastic anemia, occurs when the individual has a rare disorder in which the body has difficulty absorbing vitamin B-12, according to the U.S. National Institutes of Health at its MedlinePlus website. Normally, a protein called intrinsic factor attaches to vitamin B-12 in the stomach, which allows the intestine to absorb this vitamin. In some people, the body destroys the stomach cells that release intrinsic factor. Treatment for pernicious anemia commonly includes vitamin B-12 injections.
Vitamin B-12 is essential for central nervous system function -- neurological symptoms are also connected with low vitamin B-12 levels. Symptoms can include numbness or tingling sensations in the feet and hands, balance problems, confusion, depression, poor memory and even dementia. Early treatment with vitamin B-12 injections is important to prevent permanent damage, advises MedlinePlus.
An article published in the February-March 2004 issue of the "Townsend Letter for Doctors and Patients" notes that most doctors believe vitamin B-12 injections taken for energy boosting only have a placebo effect unless the individual is deficient in this vitamin. The article discusses a study which provides contrasting evidence. Twenty-eight participants complaining of fatigue but having normal levels of vitamin B-12 and hemoglobin, the primary component of red blood cells, were enrolled. About half the group received vitamin B-12 injections for two weeks, took a break for two weeks, then received placebo injections for an additional two weeks. The other participants received the placebo first. Those who received placebo first experienced a significant response to vitamin B-12 in the indicators of well-being and happiness, with borderline significant improvement in fatigue and appetite. When vitamin B-12 was provided first, improvements were similar, but no difference occurred between the response to the vitamin and the placebo. The authors concluded the effects of vitamin B-12 lasted long enough to cause these results. The conclusion was supported by blood tests showing continued elevation of vitamin B-12 levels four weeks after the last injection.