Many people turn to caffeine in the form of teas, coffees, and energy drinks. These methods may provide temporary relief, but if you feel tired because of a B-12 deficiency, caffeine won't solve the underlying problem. Lack of energy due to a B-12 deficiency is more common than you think. Nearly 40% of Americans are deficient in vitamin B-12.[1] Since this B vitamin takes part in the production of red blood cells, nerve sheaths, and DNA, you'll benefit from more than just improved energy levels.[2] Many people have returned their B-12 levels to normal after being deficient for years. They report feeling more energized and mentally sharp. If you've ever considered taking a B-12 supplement to improve your thinking or wellness, then read on.