Diabetes and urine glucose monitoring
Although used in the past to self-monitor diabetes control, urine glucose testing has been largely replaced by self blood glucose monitoring using a small, personal meter.
The reason for this is the greater accuracy with which blood glucose monitoring reflects your blood glucose level.
However, if you have difficulty obtaining a drop of blood, or you have some other difficulty performing blood glucose monitoring, your doctor or diabetes educator may suggest that urine glucose monitoring is suitable for you.
What does urine glucose testing measure?
A urine glucose test determines whether or not glucose (sugar) is present in the urine.
Glucose will overflow into the urine only when the blood glucose level is high, that is, too high for the kidneys to stop it spilling over into the urine. In most people, blood glucose levels above 10 mmol of glucose per litre of plasma will cause glucose to appear in the urine. This level is called the ‘renal threshold’ for glucose.
However, the renal threshold for glucose can be lower in some people who are otherwise healthy, during pregnancy, and in people who have a kidney disorder. In these people, glucose may be present in the urine despite the blood glucose being normal. This can sometimes make urine glucose tests difficult to interpret.
What does urine glucose testing involve?
If you are to monitor your diabetes with urine glucose testing, you will be advised which time of day to perform the test.
Make sure you understand how to perform the test, and go over the instructions for your brand of test strip with your doctor or diabetes educator.
To perform the test:
- collect a small amount of urine;
- apply this to the test strip, usually by dipping the strip in the urine sample;
- read the test result at the specified time, by comparing the colour change on the test strip with the standard colour range for your brand of test strip. The reference colour chart is usually printed on the container.
It’s a good idea to write down your test results or keep a chart of them, and take these with you when you see your doctor or diabetes educator. Also note down any special circumstances at the time of the test, for example, if you had a cold or were under some emotional stress, or were overeating or taking medication to treat another condition.
This type of information is helpful to your doctor when making decisions about how to best manage your diabetes.
Limitations of urine glucose monitoring
If monitoring your diabetes control by testing your urine glucose, it’s important to understand the limitations of this method.
- A urine glucose test does not reflect your blood glucose level at the time of testing; instead, it gives an indication of your blood glucose level over the past several hours. For example, some of the urine present in your bladder may be 2 hours old, and may show glucose even though your blood glucose may have normalised since then. Compare this to a blood glucose test which gives you a reading of your current blood glucose level.
- A urine glucose test does not give you any information about low blood glucose levels, as glucose is only found in the urine when the blood glucose level is above 10 mmol/L. That is, a negative urine glucose test may be the result of a normal blood glucose level or a dangerously low blood glucose level, with the urine glucose test unable to differentiate between the 2 situations.
- The results of a urine glucose test are influenced by the volume and concentration of urine that you pass, which will vary with the amount of fluid you consume and your fluid loss due to such things as heavy sweating or vomiting.
- Urine glucose tests designed for home use rely on interpreting a colour change to define the result. Subtle colour differences may be difficult to interpret.
- If a urine glucose test is not read at the specified time after applying the urine to the test strip, then the result is prone to error.
- Some medications may interfere with the results of urine glucose testing.
Advantages of urine glucose monitoring
- Urine glucose testing is easy to do: just dip the test strip in the urine and read the result at the allocated time.
- It is less painful than blood glucose monitoring — no finger pricks to collect blood!
- Urine test strips are less costly than buying a blood glucose monitor and its test strips.