Abstract: Detecting red blood cells in a patient's urine by placing an aliquot of the urine in an automated analyzer sampling cup. The urine is transferred to a cuvette mounted within the automated analyzer and one or more reagent compositions in an aqueous medium is injected into the cuvette. The reagent contains a buffer to adjust pH, chemicals to remove substances in the urine that interfere with colorimetric photometry, a compound to lyse the red blood cells in the urine, a substrate to react with the hemoglobin, a color indicator and a surfactant to improve fluid mechanics. The sample is read against a standard using a pre-programmed monochromatically specified wavelength to determine the presence or absence of blood cells in the patient's urine.