Sodium-glucose co-transporter-2 inhibitors (SGLT2i) are novel oral hypoglycaemic agents. For patients with diabetes mellitus, without a prior history of myocardial infarction or atherosclerotic disease, SGLT2i have been shown to reduce incident heart failure and worsening renal function. SGLT2i therapy is increasing among patients presenting for cardiac surgery. However, the perioperative use of SGLT2i carries a significant risk of euglycaemic diabetic ketoacidosis, due to their catabolic mechanism of action. This case report demonstrates euglycaemic ketoacidosis post-coronary artery bypass grafting secondary to SGLT2i, highlighting the multiple risk factors and consequences of this iatrogenic complication.