Could i still take a b12 injection if it is expired by 6months?

Expired meds: Two sides to this answer - the "legal" side - no - medications have expiration dates for reasons of potency and sterility. Over time medicatons lose their potency and if it is a multiple dose vial - the issue of sterility comes into play. Now the "practical" answer - yes- if the vial was only used for you and the fluid appears clear it should be safe to use - the potency may be diminishe.

Yes, safe, but...: The expiration date on meds is the time limit that the dosage potency is guaranteed. After that time, the potency may be less (but often is not). It is the rare drug (some types of tetracycline) that become toxic if outdated. Nevertheless, a pharmacy can not dispense, and a physician is not supposed to administer a medicine beyond its expiration date.