Patients with type 1 diabetes adapt acutely to sustained mild hypoglycaemia.

The relationship between awareness of, and the catecholamine response to, sustained mild hypoglycaemia was examined in six well-controlled Type 1 diabetic patients (age 24-41 years, HbA1 less than 10.0%) using a hyperinsulinaemic clamp. Blood glucose was maintained at 2.8 mmol l-1 for 90 min with a euglycaemic (4.5 mmol l-1) clamp as a control. After 40 min at a blood glucose of 2.8 mmol l-1, symptom score had increased from 0.2 +/- 0.2 (+/- SE) to 3.0 +/- 0.8 (p less than 0.01), cognitive function (measured by reaction time) deteriorated by 55 +/- 20 ms, and four patients 'felt hypoglycaemic'. This was associated with a rise in plasma adrenaline from 0.48 to 1.30 nmol l-1 (p less than 0.01). However when hypoglycaemia was prolonged to 90 min, symptom score decreased to 1.8 +/- 0.2, none 'felt hypoglycaemic', and reaction time improved by 30 +/- 12 ms, despite a progressive rise in plasma adrenaline to 1.62 nmol l-1. Thus, despite high levels of adrenaline, diabetic patients develop reduced symptoms and no longer 'feel hypoglycaemic' during sustained mild hypoglycaemia.