Creatine is an amino acid made in the liver and stored in muscles. When combined with phosphate, it is a readily available source of energy in the body. In the diet, creatine is found in milk, red meat, and some fish.
People take supplements of creatine to improve physical or athletic performance and to decrease fatigue. Its use is associated with weight gain. A few studies indicate that creatine can increase the amount of work performed with a short maximal effort (for example, in sprinting). However, a few others indicate no improvement in this type of activity.