Hypoglycaemia

In the individual without diabetes, blood glucose rarely falls below the lower levels of the normal range, even during periods of fasting. This is achieved by a number of interactions between insulin, glucagon and the liver, as described in Chapter 3. However, patients taking hypoglycaemic agents that stimulate the beta cells (sulphonylureas and the prandial regulators), or who are using insulin therapy, are at risk of hypoglycaemia. They should be advised of their risk, given information about the situations that may increase their risk, be aware of the symptoms of hypoglycaemia and know how to take corrective action.

Most patients will be able to recognise the symptoms of hypoglycaemia. These symptoms can be classified as autonomic (caused by activation of the sympathetic or parasympathetic nervous system) or neuroglycopenic (caused by the effects of deprivation of glucose to the brain) (Table 8.1). If able, the patient should confirm their diagnosis by testing their blood glucose, which would be less than 4 mmol/l. (As symptoms of hypoglycaemia may be felt if the blood glucose is falling rapidly, the patient should retest after a few minutes even if the reading is above 4 mmol/l. This may happen, for example, if insulin has been injected into a muscle instead of subcutaneous fat.)

The corrective treatment for the symptoms of hypoglycaemia is to immediately eat or drink some fast-acting carbohydrate that can be quickly digested and absorbed, for example five dextrose tablets, 100 ml Lucozade or 150 ml of non-diet carbonated drink (Fig. 8.1).