Diagnosis of Diabetes

Diabetes once diagnosed is for life. The perseverance and self discipline needed over a lifetime can often tax even the most robust of people to the limit. Those caring for them also require perseverance and an understanding of humanity combined with a cautious optimism, to guide those with diabetes through the peaks and troughs of their lives.

Definition of Diabetes
Diabetes occurs either because of a lack of insulin or because of the presence of factors that oppose the action of insulin. The result of insufficient action of insulin is an increase in blood glucose concentration (hyperglycaemia). Many other metabolic abnormalities occur, notably an increase in ketone bodies in the blood when there is a severe lack of insulin.

Diagnosis of diabetes

The diagnosis of diabetes must always be established by a blood glucose measurement made in an accredited laboratory.

Glucose tolerance test
The glucose tolerance test is not normally needed in routine clinical practice, and then only if uncertainty exists in younger patients, or to establish an exact diagnosis in pregnancy. For reliable results, glucose tolerance tests should be performed in the morning after an overnight fast, with the patient sitting quietly and not smoking; it is also important that the patient should have normal meals for the previous three days and should not have been dieting.

False results may also occur if the patient has been ill recently or has had prolonged bed rest. Blood glucose concentrations are measured fasting and then one and two hours after a drink of 75 g of glucose in 250-350 ml water (in children 1•75 g/kg to a maximum of 75 g), preferably flavoured, for example, with pure lemon juice. Urine tests should be performed before the glucose drink and at one and two hours. Interpretation of blood glucose values according to WHO criteria is shown in the table.

Adapted from Diabetes Care 1997;20:1183-119