Vitamin B-12 injections are beneficial for people with low levels of the vitamin. For people with normal levels of the vitamin, injections are not necessary, according to Shape.
For people with a B-12 deficiency, a regular injection of B-12 provides benefits such as an increase in energy. If a person's B-12 levels are normal, on the other hand, B-12 injections do not provide benefits and thus are unnecessary. This is because B-12 is a water-soluble vitamin, which means that the body only requires a certain level and eliminates any excess levels of the vitamin. Thus, B-12 injections provide no benefits for individuals who already have the required amount, states Shape.