A verterinarian told me they give b12 injections to animals to gain weight? why then are b12 injections given to lose weight in humans?

No wt loss w/B12: I can't speak for veterinary medicine as I am not a veterinarian. However, as a family physician, i can assure you that i don't give B12 injections to cause weight loss in humans as there is no such link between the two. In other words, taking B12 whether as a shot or pill will not lead to weight loss. If you're low in b12, you may need B12 pills or shots, but that won't cause weight loss.

Misconception: B12 will not cause you to lose weight. Unfortunately, that is a common scam in some places, particularly here in south florida. In fact, there are efforts to curb that with laws in florida. There is no evidence that B12 actually leads to weight loss.