Creatine is used as a dietary supplement to increase muscle mass and improve exercise performance. Creatine is a normal component of human milk, supplying about 9% of the infant’s daily requirements, although the amount varies by country and ethnicity.[1,2] Creatine levels are highest in colostrum, with levels decreasing over the first 2 weeks postpartum before stabilizing.[3] Milk levels of creatine have not been measured after supplementation in humans. Creatine blood levels are lower in vegan than omnivorous mothers.[4] Some authors speculate that creatine supplementation of nursing mothers might help avoid creatine deficiency syndromes, but no studies are available that test this hypothesis.[5] Creatine is converted into creatinine in the mother's and infant's bodies. It can increase the infant's serum creatinine, which may alter estimations of the infant's kidney function.[6] Until more data are available, it is probably best to avoid creatine supplementation unless it is prescribed by a healthcare professional.