Common problems with vitamin B-12 injections include side effects, such as rash, itching, diarrhea, swelling and rapid weight gain, reports Drugs.com. Those who self-inject the medication must learn to administer injections properly and safely dispose of the empty syringes. There is a possibility of more serious side effects, and pregnant and nursing women should consult their doctors before receiving the injections to discuss possible risks to babies.
Vitamin B-12 injections effectively help people with pernicious anemia and vitamin B-12 deficiency, explains MedlinePlus. Those with inherited vitamin B-12 deficiency, known as Imerslund-Grasbeck disease, sometimes have vitamin B-12 injections monthly for their entire lives after diagnosis. The U.S. Food and Drug Administration also approves vitamin B-12 injections following cyanide poisoning. Sufficient evidence of effectiveness does not exist for other uses of vitamin B-12 injections. People normally take vitamin B-12 in foods, supplements, nose gels and skin creams.
Vitamin B-12 injections are safe for most people unless they have Leber's disease or are allergic to cobalt or cyanocobalamin, which is the synthetic vitamin B-12 that the injections contain, according to Drugs.com. Patients should alert their doctors before initiating injections if they have infections, sinus conditions, iron deficiency, liver disease or kidney disease. They should carefully follow dosage instructions and avoid heavy alcohol use while taking the injections.