Vitamin B12 is a water soluble vitamin. There are no apparent side effects of vitamin B12 when it is taken orally in recommended doses. When it is received intramuscularly by means of injection, such as in a cyanocobalamin injection, or sublingually, through the tissues beneath the tongue, doses are often much higher and side effects may occur. These are very rare and range from minor problems, such as headache and mild digestive issues, to more serious side effects, such as breathing difficulties and heart problems.
The most common side effects of vitamin B12 injections are usually not serious. Some individuals who receive an injection may experience tenderness, or feel a burning sensation in the vicinity of the injection site. Some may suddenly feel as though they have swelling all over the body, experience headaches, joint pain, or begin to have stomach problems, including nausea and diarrhea. An individual who experiences these symptoms should contact a physician if the side effects of vitamin B12 do not disappear after a short period of time.
Other side effects of vitamin B12 can be more serious, but are not as common. Those who receive injections have a slight chance of experiencing symptoms similar to those of a cardiac event, such as heart palpitations, a more rapid heartbeat, chest tightness, or chest pains. Side effects of vitamin B12 can also include symptoms similar to those of a cold, such as coughing, low energy, wheezing, and breathing difficulties after minor physical exertion or after lying down. Other rare side effects of vitamin B12 involve the muscles, including muscular cramps, muscle weakness, muscle soreness, and tingling. People who experience these serious side effects should see a physician right away.
Some vitamin B12 side effects can involve the skin, including rashes, hives, itching, and redness of skin all over the body, especially the face. Leg tenderness has also occurred as the result of vitamin B12 injections. Swelling can occur in one leg or in the feet, ankles, arms, and hands.
It is possible for individuals to gain weight rapidly after vitamin B12 treatment. They may also need to urinate frequently, feel exceptionally thirsty, have difficulties swallowing, and experience confusion, numbness, dizziness, and tingling. It is not entirely known whether side effects of vitamin B12 occur due to high doses of this vitamin or due to other ingredients that may be added to the supplement formula.
Vitamin B12 can interact with a variety of drugs. Folic acid and vitamin B12 work together in the body and are commonly taken together, but a reaction can occur if too much of one is taken. Other drugs vitamin B12 may interact with include certain kinds of antibiotics, Phenobarbital, potassium supplements, alcohol, and others. Those who take vitamin B12 supplements or injections should let their health care provider know about all prescription medications, over-the-counter medications, vitamins, herbal remedies, and any other substances they consume on a regular basis.
