Unrecognised nocturnal hypoglycaemia masquerading as senile dementia.

A 70-year-old woman with insulin dependent diabetes mellitus presented with symptoms suggestive of senile dementia. Outpatient assessment failed to reveal poor diabetic control with frequent nocturnal hypoglycaemia. Eventual appreciation of the poor control resulted in several failed attempts at improving therapy with various subcutaneous insulin regimes. Intramuscular and intravenous routes produced acceptable blood glucose levels with striking reversal of the patient's symptoms. The possible causes of nocturnal hypoglycaemia in this patient are discussed.