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Vitamin B12 by Subcutaneous Injection

By Sarah Terry

Also called cobalamin, vitamin B12 is an essential nutrient that your body needs for a variety of important functions. B12 injections are a special form of the vitamin called cyanocobalamin, which is synthetic. You might need vitamin B12 injections if you have a serious deficiency or related medical condition such as pernicious anemia. Talk with your doctor about the risks and benefits of vitamin B12 injections.


Vitamin B12 works to support your nerve cells, create S-adenosylmethionine – SAMe – and regulate homocysteine levels in your blood, says the University of Pittsburgh Medical Center. Specifically, vitamin B12 is essential to metabolizing amino acids and fatty acids in your cells, as well as to create nucleic acid for DNA, notes the Memorial Sloan-Kettering Cancer Center. You can get vitamin B12 from your diet, particularly from eating meats, fish, poultry, dairy products and fortified cereals, and natural bacteria in your body also synthesize B12. Just like vitamin B12, the injection form called cyanocobalamin works to support healthy blood composition and cell reproduction in your body, states the University of Michigan Health System.


Vitamin B12 injections are most often used to treat pernicious anemia, a condition involving vitamin B12 malabsorption, says the University of Michigan Health System. Cyanocobalamin injections can also help treat vitamin B12 deficiencies related to other medical conditions such as shingles or postherpetic neuralgia, tinnitus, seborrheic dermatitis and dermatitis herpetiformis.


Large doses of oral vitamin-B12 supplements could provide similar benefits as subcutaneous injections of the vitamin. For example, treatment of pernicious anemia is sometimes carried out using oral vitamin B12 supplements instead of injections, says the University of Michigan Health System. In addition to treating a deficiency, vitamin B12 supplementation is also sometimes recommended for helping to treat restless leg syndrome, Lou Gehrig’s Disease, asthma, periodontal disease, diabetic neuropathy and osteoporosis, notes the University of Pittsburgh Medical Center. Vitamin B12 might help treat eczema, depression, Bell’s Palsy, vitiligo and Alzheimer’s disease, as well as to support HIV treatment. Additionally, vitamin B12 may play a role in treating cardiovascular disease, lung or breast cancer, sleep disorders, strokes and fatigue, states the Memorial Sloan-Kettering Cancer Center. Don’t take vitamin B12 supplements to treat or prevent any medical condition before first consulting your physician.

Side Effects

While receiving vitamin B12 injections, you could experience side effects such as pain, redness, itching or swelling at the injection site, as well as stomach upset, diarrhea, nausea, dizziness and headache, says the University of Michigan Health System. Other common side effects include joint pain, weakness, numbness and rash. In rare cases, dangerous allergic reactions can occur due to vitamin B12 injections, so seek immediate medical attention if you have symptoms such as swelling of your face or mouth, difficulty breathing and hives.


Don’t have vitamin B12 injections if you have Leber’s disease, because the supplement could cause severe nerve damage in your eyes and even blindness, warns the University of Michigan Health System. Also, avoid consuming excessive amounts of alcohol while you’re receiving vitamin B12 injections. Oral vitamin B12 and cyanocobalamin injections could potentially interfere with certain medications such as AZT, colchicine, oral diabetes drugs and stomach-acid reducers, cautions the University of Pittsburgh Medical Center. All of these medications can inhibit your body’s absorption of vitamin B12.

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