Diabetic ketoacidosis (DKA) is a life-threatening consequence of diabetes mellitus. Infection is the most common cause of DKA. A 41-year-old man came to the hospital emergency department with shortness of breath the day before, nausea, vomiting, coughing, pain and swelling in the left neck. The patient has a history of uncontrolled diabetes. A physical examination revealed Kussmaul's breathing and a lump the size of a tennis ball on the left side of his neck. Laboratory findings are: leukocytosis, an increase in blood sugar of 512 mg/dL; blood gas analysis shows acidosis, ketone examination reveals ketonuria; Electrocardiography shows waves of ischemic heart disease, with elevated Hs Troponin. Fine needle examination of the lump shows a neck abscess. The patient was diagnosed with DKA in type 2 diabetes mellitus, with the acute coronary syndrome and neck abscess. Surgical debridement, antibiotics, acute coronary syndrome therapy, and DKA therapy are treatments. The patient responded well to treatment.