Vitamin B12 injections are used to treat and prevent severe B-12 deficiencies, pernicious anemia, and poor gut absorption. Usually prescribed as cyanocobalamin or hydroxocobalamin, they are typically administered into a muscle (intramuscularly) or under the skin (subcutaneously) by a healthcare provider. [1, 2, 3, 4, 5]

Because the injection bypasses the digestive tract, it provides a direct, rapid way to raise blood levels of the vitamin. Many people also use it as a supplement to help combat fatigue, increase energy, and support metabolism.