For more than 50 years the detection of reducing substances in urine has been a standard laboratory procedure. For the inborn errors of carbohydrate metabolism, it is used as a screening test. Specifically for screening galactosaemia (galactosuria), this test is performed. A combination of enzymatic dipstick assay for urinary glucose can detect inborn errors of sugar metabolism in pediatric patients. A negative dipstick glucose assay and a positive reducing test suggest that some other substances other than glucose are also present in the urine.