Methylcobalamin Side Effects

Methylcobalamin is another name for Vitamin B12, a substance found naturally in meat, milk and fish. Because Vitamin B12 is important to nervous system to functioning and the process of blood cell formation, people with deficiencies of the vitamin are commonly treated with B12 Methylcobalamin supplements; however, these supplements pose a risk for side effects in some patients.

Types of Side Effects

• Possible side effects of Methylcobalamin include itching and diarrhea or loose stools. Patients who use skin creams for psoriasis that contain B12 are more likely to develop itching than those using oral supplements to treat a vitamin deficiency, according to RxList.

Allergic Reactions

• Though uncommon, some people develop allergic reactions to Methylcobalamin, causing shortness of breath, hives, wheezing, chest pain and swelling of the face or extremities, according to the Physicians Desktop Reference. Because allergic reactions have the potential to develop into life-threatening conditions like shock, seek emergency medical attention if you develop any allergy symptoms while taking Methylcobalamin.

Risks

• Rarely, Methylcobalamin causes the formation of blood clots, leading to life-threatening events like pulmonary embolisms, stroke and heart attacks, cautions RxList.

Drug Interactions

• Because the antibacterial drug Chloramphenicol interferes with the action of B12 supplements, avoid use of Methylcobalamin if you are given a prescription for the antibiotic.

Considerations

• Although Methylcobalamin has no known adverse effects on fetal development, discuss with your doctor what dosage you should be taking if you are pregnant. If you have a medical history of blood clots, Leber's Disease, anemia or any disorder that causes an excessive amount of blood cells like polycythemia vera, it may not be safe for you to take B12 supplements due to possible side effects.