Sickle cell trait (SCT) has a UK urban population rate estimated at 3.2%. The condition may remain unrecognised, but sudden death is a recognised feature. The sudden death of a 51-year-old man with SCT who presented with hyperosmolar non-ketotic acidosis (HONK) as his first presentation of diabetes is reported here. After admission to hospital, a rapid deterioration was seen in his condition, with loss of cardiac output, leading to death. He was found to have had acute-chest syndrome and hepatosplenic infarction on postmortem examination. The pathophysiology of sudden death in patients with SCT and the role of HONK in the patient’s demise is discussed here.