More and more people are being told that they are B12 deficient, and a deficiency in B12 can result in mood swings, poor sleep, extreme fatigue, muscle weakness, vision problems, and processing difficulties. A B12 injection is an incredibly effective way to optimise B12 levels, is virtually painless, and the long-lasting benefits are felt incredibly quickly. As B12 is a water-soluble vitamin, any excess which the body does not require is safely excreted.