Glucose, 24 Hour, Urine
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Under normal circumstances, glucose is readily filtered by glomeruli and the filtered glucose is reabsorbed by the proximal tubule; essentially no glucose is normally excreted in the urine. However, the capacity for the proximal tubule to reabsorb glucose is limited; if the filtered load exceeds the proximal tubule's reabsorptive capacity, a portion of the filtered glucose will be excreted in the urine. Thus, elevated serum glucose concentrations (such as occur with diabetes mellitus) may result in an increase in filtered load of glucose and may overwhelm the tubules' reabsorptive capacity resulting in glucosuria.
Additionally, conditions which adversely affect proximal tubule function may also result in decreased reabsorption of glucose, and increased urinary glucose concentration, even in the presence of normal plasma glucose concentrations. Some of these conditions include Fanconi syndrome, Wilson's disease, hereditary glucosuria, and interstitial nephritis. These conditions are relatively rare, and most causes for elevated urine glucose concentrations are due to elevated serum glucose levels.
Limited usefulness in the screening or management of diabetes mellitus
Elevated urine glucose concentration reflects either the presence of hyperglycemia or a defect in proximal tubule function.
As a screening test for diabetes mellitus, urine glucose testing has a low sensitivity (though reasonably good specificity).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Urine glucose monitoring for the management of diabetes mellitus has essentially been replaced by more accurate and reliable blood glucose determinations.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
< or =0.15 g/24 hours
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Tietz Textbook of Clinical Chemistry. Edited by CA Burtis, ER Ashwood. Third edition, Philadelphia, PA. WB Saunders Company, 1999