What side effects can this medication cause?
If you experience any of the following serious side effects, stop taking cyanocobalamin and seek emergency medical attention:
an allergic reaction (difficulty breathing, closing of your throat, swelling of your lips, tongue, or face, or hives)
chest pain or difficulty breathing
unusual warmth, redness, or pain in an arm or leg
Other less serious side effects may be more likely to occur. Continue to take cyanocobalamin and talk to your doctor if you experience:
headache
upset stomach or diarrhea
numbness or tingling
fever
dizziness
felling of swelling of entire body
itching
rash
Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.
Why is this medication prescribed?
Dosage and using this medicine
What special precautions should I follow?
What should I do if I forget a dose?