what does the b12 injection help with Vitamin Dosage B12 Shots at Home: How,

Common side effects include, but may not be limited to: pain or redness at the injection site mild diarrhea pruritus (itching) increased swelling joint pain dizziness headache nervousness or anxiety Serious side effects may include: allergic reactions peripheral vascular thrombosis hypokalemia (low potassium levels) pulmonary edema (fluid build-up around or in the lungs) thrombocytosis congestive heart failure There have been reports of anaphylactic shock and death after the parenteral administration of vitamin B12

And it makes it very hard to to apply a blanket rule - some people may manage well with alcohol and injections

When nerve fibrils are stretched, mild pain results

Injections of B12 may be given to patients who are unable to absorb this vitamin in their bodies due to problems such as gastrointestinal pathology or dysfunction