Glucosuria

Although small amounts of glucose are present in the urine of all normal individuals, the term glucosuria is conventionally reserved for pathologic amounts of urine glucose (more than 25 mg/dl in random fresh urine). The renal tubule will reabsorb almost all the glucose present in the normal glomerular filtrate. Glucosuria occurs when that balance is lost: when the amount of glucose in the glomerular filtrate exceeds the capacity of the renal tubule to reabsorb it. The balance can be lost either when the plasma glucose is elevated (e.g., in diabetes mellitus) or when the absorptive capacity of the tubule is impaired (e.g., in Fanconi syndrome, pregnancy, hereditary renal glucosuria, and acute tubular injury).