For your health and wellbeing, as well as the longevity and effectiveness of your treatment, please read and understand the below fully.
There is risk of mild diarrhea, upset stomach, nausea, a feeling of pain and a warm sensation at the site of the injection, a feeling, or a sense, of being swollen over the entire body, headache, joint pain and breakouts.
Although rare, Vitamin B12 injections can result in serious side effects. Although this is a relatively rare occurrence, anyone taking vitamin B12 injections should be aware of the possibility. Uncommon side effects are much more serious than the common side effects of B12 injections, and such side effects should be reported to a physician to be evaluated for seriousness.
Uncommon and dangerous side effects include: rapid heartbeat, chest pain, flushed face, muscle cramps and weakness, difficulty breathing and swallowing, dizziness, confusion, rapid weight gain, tight feelings in the chest, hives, skin rashes, shortness of breath when there is no physical exertion and unusual wheezing and coughing. If you experience such side effects, seek medical advice from your local pharmacy, doctor or A&E Department.