Urine testing in diabetes

Urine can be tested for:

• glucose
• ketones

Testing of urine for glucose is by means of reagent strips which utilise the glucose oxidase reaction to produce a colour change which is interpreted manually. Measurement of urinary glucose is a crude measure of control for two main reasons:

• the renal threshold for glucose, which determines the plasma glucose level at which glycosuria occurs, varies between individuals from 7 to 12 mmol/L.
  
  
• the level of glycosuria does not represent plasma glucose levels at the time of testing but an average of the plasma glucose level since the patient last voided. This problem can be partially overcome by the technique of double-voiding where the patient empties the bladder and then collects a second sample for analysis shortly afterwards.

There is no evidence that blood testing is more effective than urine testing at improving blood glucose control in people with type II diabetes (1).

However, self-monitoring via blood testing is likely to be most appropriate for patients with type I diabetes or type II diabetes who use insulin, who adjust their dose as a result of the test, or for all patients with diabetes when they have an intercurrent illness (1).

Urine tesing for ketones should be carried out by type I diabetics who are unwell or who are hyperglycaemic for a significant period of time. To this end some blood glucose metering devices automatically suggest measurement of urinary ketones when the blood glucose is above a certain threshold. The presence of ketones in the urine is indicative of serious metabolic abnormality.

Notes:

• testing for the presence of microalbuminuria is achieved via the urine-albumin-creatinine ration (see linked item)

Reference:

1. MeReC Bulletin (July 2002), 13(1),1-4.