Acute hypoglycaemia may present with adrenergic symptoms, such as sweating, palpitations and tremor, or neuroglycopaenic symptoms such as cognitive impairment or ataxia. Symptoms occur with a plasma glucose less than 2.5 mmol/L and resolve on glucose administration. The commonest problem in evaluating such patients is that a blood sample is not taken at the time of hypoglycaemia for estimation of insulin and other analytes (see below). After excluding iatrogenic hypoglycaemia in patients with diabetes, the commonest cause of acute hypoglycaemia is alcohol intoxication.
More commonly patients present subacutely with episodes of cognitive impairment or presyncopal symptoms, which often resolve with carbohydrate ingestion. In these patients three 16 hour fasts are probably as effective at eliciting evidence of hypoglycaemia as the traditional 72 hour fast, using a blood glucose less than 3 mmol/L as diagnostic evidence and adding ketone body estimation to the diagnostic evaluation.
- Marks V, Teale JD. Investigation of hypoglycaemia. Clin Endocrinol (Oxf) 1996;44:133-136.