Creatine is an amino acid found primarily in the muscles and brain. Although it can be synthesized, most people get creatine from seafood and red meat. The body converts creatine into phosphocreatine and stores it in the muscles, where it is used for energy. Therefore, people take creatine supplements orally to improve athletic performance and increase muscle mass.

Glomerular filtration rate is a value that helps assess and determine existing kidney damage. The higher the glomerular filtration rate, the better the kidneys work. There are many ways to calculate glomerular filtration rate such as calculating by blood creatinine, based on the MDRD formula,...