Urine testing provides only historical information

Editor—Marilyn Gallichan raised some important issues concerning self monitoring of blood glucose concentrations but greatly underestimated its benefits in terms of health, safety, and quality of life to patients taking insulin.1 The hypoglycaemic potential of insulin is a constant worry to all patients with insulin dependent diabetes, but hypoglycaemia can be confirmed only if blood is tested. Urine testing will not help.

The comparison between the merits of testing blood glucose with those of testing urine glucose missed the point that the two tests provide quite different information and should not be regarded as old versus new or accurate versus inaccurate. Urine tests are relatively cheap and easy to use, but their interpretation for patients with insulin dependent diabetes requiring tight control is difficult because glucose can often be found in the urine at the same time as the patient has hypoglycaemia.

While urine testing can be helpful, patients need to be taught that it provides historical information. Thus data from urine tests on one day can be used to predict the next day's treatment and dietary and activity schedules but should never be used to determine current action.

Blood testing is of benefit not only when unexpected variations occur but also for those patients who are prepared to perform tests in order to “see” and thus learn about how their metabolism deals with individual meals and activities. Exercise has profound effects, particularly on those patients who are taking insulin. Blood testing before and after sport is essential if hypoglycaemia is to be avoided.

Gallichan quotes a patient who said “I do not worry about my day to day control provided the [haemoglobin A1] readings stay good” this is a flawed philosophy. Many patients have only annual measurements of haemoglobin A1. Is it acceptable for patients to tolerate poor …