The problem of detecting whether a urine sample is true human urine or a counterfeit urine product is solved by the use of reagent systems that detect two markers normally present in human urine. The markers acid phosphatase and alkaline phosphatase catalyze the substrates thymolphthalein monophosphate and p-nitrophenol phosphate, respectively. These substrates are formulated as spot tests on a dip stick or as reagents for use in automated chemical analyzers. The presence of the markers can be qualitatively detected by color-changes in the sample, formed by the pH-specific chromogens that result from catalysis of the substrates with the markers. The control reagent can further indicate whether a counterfeit urine product contains one or both of the chromogens.