Urine Glucose Testing
The basis for using glucose tests is the renal threshold for glucose which is roughly correlated with hyperglycemia; thus, urine tests for the presence of glucose, may have a role to play in monitoring glycemic control, if the renal threshold of the patient is normal and stable.
Unfortunately, some patients with raised blood glucose levels may show no urine glucose, whilst others with a normal blood glucose may show evidence of glucose in the urine.
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Inspite of these limitations, urine glucose testing continues to be widely used to assess diabetes control.
In patients with a "normal" renal threshold, and being treated with diet alone, or diet and small doses of OHAs, it is desirable to get all the urine samples (pre-and post-prandial) glucose free.
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In patients on insulin, one should try to get all the pre-prandial urine samples free of the presence of glucose.
If urine glucose tests are used to monitor glycemic control, one must be aware of the limitations:
- In many cases, marked hyperglycemia may occur without glucosuria and conversely, significant glucosuria may be seen with euglycemia.
- The urine glucose levels do NOT correspond to the prevailing blood glucose levels at the moment of testing.
- A negative test does NOT distinguish between hypoglycemia, euglycemia and mild to moderate hyperglycemia.
- Urine glucose tests do NOT give warning of impending hypoglycemia.
Urine glucose testing given its limitations, should NEVER be used alone to assess glycemic control or make changes in the management. If used, it should always be supplemented by periodic blood glucose tests.
- If urine glucose remains consistently very high, one should always check the blood glucose levels immediately.
- Conversely, in the presence of a very high blood glucose values, the urine should be checked for the presence of acetone.
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MONITORING GLYCEMIC CONTROL