Deca Durabolin injection contains the active ingredient nandrolone decanoate, which is a type of medicine called an anabolic steroid. Anabolic steroids have the same properties as the natural hormone testosterone. They are believed to increase the production of protein by the body and to enhance muscle development. Nandrolone also causes masculinisation in men who are deficient in natural male hormones, however in men with no testosterone deficiency, it actually reduces sperm production. Nandrolone injection is licensed to treat osteoporosis in women who have passed the menopause, however, this is no longer a recommended treatment for osteoporosis. In osteoporosis there is loss of bone tissue, resulting in bones that are brittle and liable to fracture. Nandrolone works by influencing the metabolism of calcium (an important constituent of bone and teeth) and thereby increasing bone mass in women suffering from osteoporosis. This makes the bones stronger and less likely to break. Deca Durabolin injection contains nandrolone decanoate in a peanut oil (arachis oil) base, which releases the active ingredient slowly over a period of up to three weeks. This is known as a "depot" injection. The injection is given into a muscle (usually the buttock) every three weeks.