Insulin degludec overdose may lead to long-lasting hypoglycaemia through its markedly prolonged half-life.

BACKGROUND: Overdose of insulin often causes long-lasting severe hypoglycaemia. Insulin degludec has the longest duration of action among the available insulin products; thus, an overdose of insulin degludec can lead to long-lasting hypoglycaemia. In the present paper, we report the case of a woman with long-lasting hypoglycaemia attributable to insulin degludec overdose and markedly prolonged insulin degludec half-life.

CASE REPORT: A 64-year-old woman with Type 2 diabetes receiving insulin therapy was taken to an emergency department because of disturbed consciousness 21 h after self-injection of 300 units of insulin degludec (4.34 units/kg). Her plasma glucose level was 2.3 mmol/l. She received repeated intravenous boluses of dextrose for 43 h with continuous intravenous dextrose infusion, but no improvement in long-lasting hypoglycaemia or consciousness was observed. Considering the possibility of adrenal insufficiency, intravenous dexamethasone was administered, and her plasma glucose levels subsequently remained above 5.5 mmol/l without intravenous dextrose boluses. She gradually regained consciousness. A total of 34 h after the overdose, her plasma immunoreactive insulin levels were markedly increased and then gradually declined over ~400 h. The insulin degludec half-life was 40.76 h.

CONCLUSION: Although the reported half-life of insulin degludec in the body is ~25 h when administered in standard doses (0.4-0.8 units/kg), no study has investigated its half-life after overdose. In the present case, the half-life of insulin degludec was ~1.6 times longer than that observed with standard doses, probably leading to long-lasting hypoglycaemia. Physicians should be aware of the possibility of unexpected long-lasting severe hypoglycaemia resulting from insulin degludec overdose.