Objective:To report one case of diabetic ketoacidosis complicated by acute myocardial infarction and upper gastrointestinal bleeding, and make a certain summary to its diagnosis and treatment in order to improve the treatment of these critically ill patients.Methods:One patient was admitted to Guizhou Aerospace Hospital on November 14, 2021 due to fatigue and vomiting for 2 days, and worsened symptoms accompanied by poor consciousness for 1 day. The patient was diagnosed with diabetic ketoacidosis complicated by acute myocardial infarction and upper gastrointestinal bleeding. The clinical symptoms, signs, laboratory examinations, and follow-ups of the patient were analyzed systematically and retrospectively.Results:After volume state assessment using a combined way, the patient was treated with appropriate fluid replacement, hypoglycemic, antiplatelet, anticoagulant, and acid inhibition strategies. After treatment, ketoacidosis and upper gastrointestinal bleeding were corrected, blood glucose gradually stabilized, and myocardial necrosis markers troponin and N-terminal brain natriuretic peptide precursor became normal.Conclusion:Treatments of diabetic ketoacidosis, acute myocardial infarction, and upper gastrointestinal bleeding are contradictory. Therefore, analyzing this patient's diagnosis and treatment is of great significance for improving treatment and reducing the mortality of these critically ill patients.