A pilot study of vitamin B12 in the treatment of tiredness

1. Twenty-eight subjects complaining of tiredness completed a double-blind cross-over trial of injections of hydroxocobalamin (5 mg twice weekly for 2 weeks) followed by a rest period of 2 weeks and then a similar course of matching placebo injections. Symptoms were assessed by a daily self-rating method and included appetite, mood, energy, sleep and general feeling of well-being. 2. Those subjects who received the placebo in the first 2-week period showed a favourable response to hydroxocobalamin in the second period in all measurements made. The response achieved statistical significance (P = 0·006) in respect of general well-being; ‘happiness’ achieved a value of P = 0·032. Subjects who received hydroxocobalamin in the first period showed no difference between responses to active and placebo treatments, which suggests that the effects of the vitamin may persist for a period of at least 4 weeks.