Creatine monohydrate is a dietary supplement used by body builders to help increase muscle mass. Many people are using this supplement to see if it helps with nerve and muscle disorders. Dietary supplements are not regulated by the Food and Drug Administration. The investigators say that, since there may be significant side effects from this supplement, especially in children, they are undertaking this study to determine the safety of this treatment.

Participants will be admitted to the University of California at San Francisco (UCSF) Children’s Hospital for three overnight visits in a three-month period. This will take place at the start of the trial, after one month of creatine supplementation and after being off creatine for one month. All participants will receive creatine.

After each six patients enrolled in the study, the dose of creatine given to the participants will be increased. The creatine is given four times a day for a five-day loading period and then once a day for the rest of the month.

During each hospital stay the participants will undergo strength and function testing. Basic blood tests will be performed once during each admission, and urine will be collected for 24 hours. Participants will not be compensated.

The children must

• be between 4 and 18 years old
• have a confirmed neuromuscular disease
• have never taken creatine supplementation
• have no kidney problems