Yes, Creatine is used alot in body building. It is also found, in large amounts, in red meat. Creatinine, the metabolite of Creatine, is produced by the mussles as a byproduct of Creatine. It is checked for in the sample validity test to insure it is indeed urine, and not colored water, Mountain Dew, or other urine looking liquids that have in the past been used as urine substitutes. In my self testing, my Creatinine levels normally range in the 230mg/dL level, but I can concentrate those levels upwards of 350ng/dL (by dehydrating myself). Add to that I am a vegetarian, so meat eaters will likly be higher and body builders, much higher. In the validity test, a minimum of 20mg/dL must be measured or the sample may be concidered 'dilute' and if the levels are below 5mg/dL, the sample may be concidered 'substitute'. There is no maximum level for Creatinine in the validity check so use as much as is recomended in the Creatine supliments directions for use. Hope that helps. N2