Some of the serious side effects of Vitamin B12 include serous allergic reaction, narrowing or blocking of blood vessels, thrombocytosis (a disorder where your body produces too many platelets), low potassium levels in body, pulmonary edema (a condition where there is excess fluid in the lungs) and congestive heart failure
You need a valid prescription from a qualified healthcare professional
Malignancy of pancreas or bowel
It is an unapproved substance
There are a few common, mild side effects associated with B12 shots, including: Mild diarrhea, itching, nausea and vomiting, dizziness, headaches, and hot flashes Redness or swelling at the injection site Temporary soreness at injection site Serious side effects are rare but require immediate medical attention