We have had several athletes at Stockton experience severe cramps that resulted in muscle strains and significant loss of playing time. Unortunately, there are no research studies dealing with these problems. However, there is no way to determine if creatine actually was the cause of these injuries. There are also potential effects of creatine on the kidneys. Particularly there is concern during the loading phase when urinary creatine excretion increases as much as 90x s.
More research needs to be done here, though.
Presently athletes with preexisting kidney disease or diabetes should avoid creatine supplementation. Creatine is naturally found in many places in the body, including the heart, brain, and testicles. But it is presently unknown what effect oral supplementation has on creatine concentration in the heart, brain, and reproductive organs. When creatine intake is increased with supplementation, natural synthesis is suppressed in the body. The body s synthesis increases when supplementation is decreased.