The Effect of Glimepiride Compared With Sitagliptin as an add-on Therapy to Metformin in Severe Insulin Deficiency Diabetes

Inclusion Criteria: * According to the World Health Organization (the WHO) 1999 criteria for the diagnosis of type 2 diabetes; the subtype was allocated to severe insulin deficiency diabetes (SIDD) at diagnosis using data-driven diabetes clusters APP. * Men and women aged ≥ 18 years and ≤ 75 years; * Diagnosed as severe insulin deficiency diabetes by the cluster classifier of Peking University People's Hospital at the initial stage of the disease course; * Metformin monotherapy with dosage ≥1500 mg/day for at least 8 weeks; * Diabetes duration less than 5 years; * The HbA1c value of the central laboratory before randomization: 7.0% ≤ HbA1c \<10.5% * estimated estimated glomerular filtration rate (eGFR)\>=60 ml/min1.73m2, alanine aminotransferase(ALT)\<120U/L ; * If other drugs are used during the course of the disease, these drugs should be withdrawn for more than 8 weeks; * Without acute diabetic complications at present. Exclusion Criteria: * Type 1 diabetes or other special types of diabetes mellitus; glutamic acid decarboxylase antibody (GADA) positive, the subtype was allocated to other subtypes at diagnosis using data-driven diabetes clusters APP. * Pregnancy or have a pregnancy plan within a year; * Lactation or have a lactation plan within a year; * Renal insufficiency, eGFR\<60; transaminase elevated, ALT\>= 120U/L; unstable coronary heart disease. * Recurrent spontaneous diabetic ketosis or uncorrected acute diabetic complications; * Participated in other clinical trials within 8 weeks before randomization; Unable to complete the study follow-up for 6 months; Have situations such as operation and need to change to insulin therapy in 6 months. * Use concomitant medication such as glucocorticoids which can affect blood sugar. * The investigator judged that it is not suitable to participate in this clinical trial.