Side Effects of B12 Shots


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November 7, 2012:
Updated With New Information.


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Why people give themselves B12 injections.

Weight loss, energy, and medical needs cited

The most common side effects of B12 injections can include nausea, an upset stomach, pain and warmth at the site of the injection, diarrhea, headaches, a sense of swelling in the whole body, and joint pain. Serious side effects require immediate medical attention and include rapid heartbeat, chest pains, palpitations, rapid weight gain (which is not what you want if you are using B12 to lose weight), swelling of the arms and legs, red face, muscle weakness, cramps, thirst, confusion, shortness of breath, dizziness, numbness and tingling, hives, itching, and rashes. Before embarking on a B12 regimen, you should tell your doctor if you are pregnant, lactating, or have liver or kidney disease.

Other conditions that should be disclosed are Leber's disease, iron deficiencies, folic acid issues, infections, bone marrow treatments (or medicines that might affect marrow) and cobalt allergies. Drug interactions with B12 can include alcohol, antibiotics like chloramphenicol, potassium, daraprim, phenytoin, phenobarbital, neomycin, and other drugs. When in doubt, you should ask a doctor or make sure that B12 (and other amino acids found in lipotropic injections) will not interact negatively with other drugs you may be taking. In any emergency situation, you should let medical personnel know that you are taking Vitamin B-12.

Notes and Special Information

Special note: The FDA has warnings about injecting B12 either on its own or as part of a "fat burning" injection that is injected into fatty tissues, but can cause abcesses and disfigurement.