Frontiers Efficacy of sublingual and oral vitamin B12 versus intramuscular administration: insights from a systematic review and meta analysis Are intramuscular vitamin B12 injections more effective than oral vitamin B12 supplementation for treating deficiency? Vitamin B12 Forms Vitamin B12 Deficiency? Heres the best way to treat it!, Many people take oral or sublingual tablets, but they may not always be effective especially if absorption is poor., The active injectable