The aim of this study is to use real-time continuous glucose monitoring (real-time CGM) system to get a 14-days blood glucose profile of the hospitalized type 2 diabetes mellitus (T2DM) patients with acute coronary syndrome (ACS), and to understand whether time in range (TIR) is associated with in-hospital outcomes of these patients. This study plans to recruit 100 patients. They will be randomly divided into 2 groups: real-time CGM group and capillary blood glucose monitoring group. All enrolled participants will receive standardized blood glucose management according to the "Expert consensus on blood glucose management of inpatients in China". The duration of the study will be 3 months. The primary endpoint is the average hospital stay and cardiac care unit (CCU) occupancy rate in T2DM patients with ACS. The secondary endpoint is a composite endpoint of nonfatal myocardial infarction, acute heart failure, heart failure rehospitalization, coronary revascularization, cardiovascular death, all-cause death.

Inclusion Criteria:

• aged ≥18 and ≤70 years old;
• T2DM according to 2022 American Diabetes Association standards;
• Patients admitted to hospital with either non-ST elevation acute coronary syndrome or ST-elevation myocardial infarction; coronary angiography examination data can be collected;
• a stable glucose lowering regimen for the previous 3 months;
• obtain informed consent;
• with complete clinical data.

Exclusion Criteria:

• Diagnosis of other types of diabetes, such as type 1 diabetes, gestational diabetes, secondary diabetes, etc.;
• No acute complications of diabetes, such as ketoacidosis, nonketotic hyperosmolar coma, etc.;
• Repeated severe hypoglycemia or hyperglycemia in the past 3 months;
• Patients who have had a history of allergic reactions to CGM materials or skin adhesives, alcohol or chlorhexidine disinfectants;
• Patients who have symptoms and signs of skin lesions, scarring, redness, infection or edema at the sensor application site that can affect the accuracy of sensor application or interstitial fluid glucose measurements;
• Combined with other acute disease states, such as uncontrolled severe infection, use of catecholamines or sedatives, use of ventilator, ventricular fibrillation, etc.;
• Patients who have a history of hematocrit, platelet, and hemoglobin abnormalities within past 2 months; moderate to severe anemia; or a disease (such as a coagulation disorder) that increases the risk of bleeding;
• Patients with malignant tumors, severe liver and kidney diseases, allergic diseases, mental and neurological diseases, combined with rheumatic or immune diseases;
• Using drugs that may affect blood sugar, including steroids, psychotropic drugs, anti-AIDS drugs, etc.;
• X-ray, CT, MRI examinations are scheduled during the period of wearing the sensor, and the appointment time cannot be changed to the beginning or the end of wearing;
• Patients currently participate in another clinical trial;
• Unwilling or unwilling to comply with study requirements, poor compliance, or refusal to use real time-CGM.