Frontiers Efficacy of sublingual and oral vitamin B12 versus intramuscular administration: insights from a systematic review and meta analysis B12 Injections vs Oral Supplements: Which are more effective? Volonte Vitamin B12 is essential for energy production, nervous system function, and red blood cell formation. However, oral B12 supplementation doesn't work well for everyoneabsorption can be limited by digestive issues, certain medications, Vitamin B12 Shots Confer No Benefit vs. a Supplement Gene Food Frontiers Efficacy of sublingual and oral vitamin B12 versus intramuscular administration: insights from a systematic review and meta analysis