b12 injection sore arm Common Side Effects From Vitamin Shots Vitamin B12 Injections in Bexley,
Description
PMID 6387014

Rubbing can irritate the area and increase your risk of infection

The maximum daily dose of a vitamin is unlikely to cause any significant side effects
Post-treatment elevation is interpreted differently from elevation without a clear exposure history

Talking to your doctor is a good place to start, as they can help you know where you stand and maybe order a blood panel for you