Efficacy of different routes of vitamin B12 supplementation for the treatment of patients with vitamin B12 deficiency: A systematic review and network meta analysis Irish Journal of Medical Science (1971 ) Efficacy of sublingual versus oral vitamin B12 supplementation for the treatment of vitamin B12 deficiencyA prospective randomised open label study Clinical Nutrition ESPEN 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 Oral vs. Intramuscular Vitamin B12 in Vitamin B12 Deficiency The Blood Project Formulation And Evaluation of Vitamin B 12 Sublingual Spray