SGLT2i are now recommended in a wide spectrum of indications including type 2 diabetes (T2DM), heart failure, and chronic kidney disease. This medication class is now available in combination with metformin, which is still a fundamental treatment in patients with T2DM. Despite excellent proven safety profile for both drugs, the expanding use of these agents in clinical practice may lead to an increased incidence of rare side effects, like metformin-associated lactic acidosis (MALA) and euglycemic diabetic ketoacidosis (EDKA), which can be life-threatening. A 58-year-old woman with T2DM and severe heart failure treated by metformin and empagliflozin developed progressive EDKA triggered by fasting that was also complicated by severe acute renal failure and MALA. She was successfully treated with intermittent hemodialysis. This case report highlights the importance of the recognition of rare, but very serious adverse effects due to combined metformin and SGLT2i therapy.