B12 is one versatile vitamin. It can increase energy, improve sleep, and alleviate stress. It can also help suppress the appetite to boost weight-loss efforts. When you get right down to it, it seems there's really nothing that B12 can't do—except maybe give you the ability to read minds. Given all this, it's no wonder that places like The B-12 Store exist. Here, clients can drop in for injections of this vitamin, which are enhanced with other supplements—including vitamin D3 and L-carnitine—designed to promote weight loss and improve overall health.