The best course of action is to load up as much as you can without causing frequent unwanted trips to the bathroom, sitting on the toilet seat. Be sure to load up 2-3 days before the U/A to allow the body to metabolize the creatine into creatinine (the end waste product found in urine that the labs check for in determining overdilution). High creatinine levels would be a non-issue to the labs because there are no upper limits established for creatinine. As long as the creatinine level is over 20 mg/dL, the urine sample is satisfactory.