A healthcare provider may teach you how to properly use the medication by yourself. The injections are prescribed by a doctor and given intramuscularly, or into muscle. A healthcare provider may teach you how to properly use the medication by yourself. Vitamin B12 shots are the most common way to prevent or treat a deficiency. Your dose needs may change if you become pregnant, if you breastfeed, or if you eat a vegetarian diet. Tell your doctor about any changes in your diet or medical condition. Because it is injected straight into the bloodstream, it can be used to supply vitamin B 12 to people who cannot absorb this vitamin … Cyanocobalamin injection is in a class of medications called vitamins. Vitamin B12 injection is injected into a muscle or under the skin. Vitamin B12 is injected into a muscle or under the skin. Your dose needs may change if you become pregnant, if you breastfeed, or if you eat a vegetarian diet. Tell your doctor about any changes in your diet or medical condition.