There are two commonly used test systems available for testing glucose in urine. These are Diastix and Diabur-Test-5000. Both work on the same principle. There is a plastic strip or stick that has a small square of chemical reagents at one end. When this is dipped in urine a reaction occurs between any glucose in the urine and the chemicals on the strip. The reaction takes a short while to develop, and at the end of that time a colour develops in the test square. This colour varies in shade and darkness according to the concentration of glucose in the urine.
By comparison of this colour with a series of colour blocks printed on the container, it is possible to judge how much glucose there is in the urine. This can be recorded either as a percentage or as an actual quantity.
Usually it is sufficient to judge if the test is negative (no glucose in the urine), a small amount or a large amount. A negative test suggests that the blood glucose is below 10 mmol/1. A small amount of glucose in urine suggests that the blood value is slightly raised. A large amount suggests that the blood glucose value could be quite high.
Urine that has been in the bladder for some time consists of urine made by the kidneys over this period. It is possible that the blood glucose value had been high earlier but has fallen to normal or low levels at the end of the period.
This would mean that the mix of urine over this period gives an average of the concentration of glucose in the urine. This could be helpful in assessing control over that period of time, but it is not particularly helpful in telling you what is happening at the time you do the test.
To avoid this problem you may be asked to test a ‘second specimen’. This means emptying the bladder and discarding this urine first. Then wait ten to thirty minutes and pass a urine sample again. This is a fresh sample representing urine made by the kidneys over the past ten to thirty minutes. It is sometimes referred to as the ‘second specimen’ and is the sample that you test.
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