Effect of Vitamin B12 Injection on the Vocal Performance of Professional Singers: A Randomized, Double-blind, Placebo-Controlled, Crossover Trial

20 active adult singers with mild vocal symptoms but no dysphonia received an intramuscular injection of vitamin B12 (1000 micrograms cyanocobalamin) and, after at least a four-week washout, placebo saline, in a double-blind crossover. At the primary 72-hour timepoint the median improvement in the Singing Voice Handicap Index-10 was 1 point (95% CI -1 to 2) after B12 versus 3 points (95% CI 0 to 4) after placebo, with no meaningful difference between them, and the same was true for the Voice Fatigue Index and Evaluation of the Ability to Sing Easily. Improvements after both injections fell short of the minimal clinically important difference, which only 4 of 20 participants reached after either injection. The authors conclude empirical B12 injections show no meaningful benefit over placebo.