How Safe Is a B12 Shot?

Vitamin B-12 injections are generally safe.
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Vitamin B-12, or cobalamin, has been called the "red vitamin" by patients who receive injections to treat B-12 deficiencies. In 2009, "Medical News Today" reported that 30 to 40 million B-12 injections are given each year in the U.S. alone, and side effects are relatively uncommon. However, the practice of giving vitamin B-12 injections is no longer as commonplace as it once was, because alternative forms of the vitamin, such as sublingual, oral and nasal preparations, are now widely available.

Vitamin B-12 Deficiency

According to "The Merck Manual of Diagnosis and Therapy," the classic form of B-12 deficiency, called pernicious anemia, is caused by a stomach condition that prevents the secretion of a special protein which is needed by your body to absorb vitamin B-12. B-12 deficiency can arise from other causes, too, such as inflammatory bowel diseases, celiac disease, pancreatic disorders or stomach surgery. Without sufficient vitamin B-12, your red blood cells do not form normally, and, if it is severe or prolonged, B-12 deficiency can lead to irreversible nerve damage.


Indications for B12 Injections

If you have a vitamin B-12 deficiency, your doctor may recommend that you receive regular injections, at least until the deficiency is corrected. Once your B-12 levels have been normalized, you may be switched to a different form of the vitamin. Although B-12 deficiency is the only real indication for receiving injections, some physicians still use vitamin B-12 injections to treat other conditions, such as fatigue. A synthetic form of vitamin B-12, called cyanocobalamin, is most commonly used in injections.

Side Effects of Vitamin B12 Injections

Common side effects associated with B-12 injections are the same as for any injection and include temporary soreness, itching, bleeding or redness at the injection site. reports that up to 25 percent of patients receiving B-12 injections develop minor side effects, such as headache, dizziness or joint pain. Much less commonly, you could develop nausea, tingling in your extremities, diarrhea or a sense of swelling. Infections are unusual, but they can occur. Rarely, severe allergic reactions, including anaphylaxis and death, have occurred.



According to, people with Leber's disease, which is an inherited eye disorder, should not get vitamin B-12 injections due to a risk for optic nerve damage and blindness in these individuals. People who are allergic to cobalt should also avoid vitamin B-12 injections. If your potassium level is low or if you have a blood disorder called polycythemia vera, your physician may choose not to administer a vitamin B-12 injection. It is not known if cyanocobalamin causes any harm to developing fetuses, so you may wish to avoid vitamin B-12 injections during pregnancy, if possible.