What side effects may I notice from receiving Cyanocobalamin (Vitamin B12)?

Side effects that you should report to your doctor or health care professional as soon as possible:
-allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
-blue tint to skin
-chest tightness, pain
-difficulty breathing, wheezing
-dizziness
-red, swollen painful area on the leg

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):
-diarrhea
-headache

This list may not describe all possible side effects for Cyanocobalamin (Vitamin B12). Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.