Subcutaneous vitamin B12 administration using a portable infusion pump in cobalamin related remethylation disorders: a gentle and easy to use alternative to intramuscular injections Orphanet Journal of Rare Diseases Springer Nature Ivy Grove Surgery : Self administration of B12 injection How Quickly Does a B12 Shot Work? No More Tired PA Relief How Long Does It Take for B12 Injections to Work? Soza Clinic How Quickly Does a B12 Shot Work? Benefits & What to Expect