Abstract: A method and apparatus for the preliminary detection of abnormal levels of metabolites in the urine of a human or mammal. The method includes the steps of determining the amount of creatinine in the urine of the human or animal, measuring the total metabolites content in the urine, using the amount of creatinine in the urine as an internal standard to compensate for variations in the urine concentration, and comparing the total metabolites content in the urine with a reference value which corresponds to the expected total metabolites content in the urine of a person or animal who does not suffer from a metabolic disorder. The apparatus (10) includes an ultraviolet oxidation unit (16) for oxidising total metabolites in a urine sample to carbon dioxide, an organic carbon stripper (18) for stripping carbon dioxide gas from the oxidised sample, and a carbon dioxide detector (69) for measuring the amount of carbon dioxide produced from the sample.