Efficacy of oral compared with intramuscular vitamin B-12 supplementation after Roux-en-Y gastric bypass: a randomized controlled trial.

Background: After Roux-en-Y gastric bypass (RYGB), patients often develop a vitamin B-12 deficiency.

Objective: Our objective was to investigate whether oral supplementation increases and normalizes low vitamin B-12 concentrations (vitamin B-12 > 200 pmol/L) in RYGB patients as compared to intramuscular injections.

Design: A randomized controlled trial in RYGB patients with subnormal serum B-12 concentrations was performed.