We have designed a clinical trial that plans to include 16 patients with stable renal allograft function, stable immunosuppressive therapy and PTDM, under standard antidiabetic therapy (exogenous insulin <40 IU). The sample size is based on a calculation assuming non-inferiority of empagliflozin monotherapy in comparison to previous insulin therapy, with respect to the primary endpoint: 2-hour blood glucose (2-h BG) during an oral glucose tolerance test (OGTT) immediately prior and 1 month after the start of empagliflozin monotherapy. The null hypothesis will be accepted if the average change in 2-h BG from the first to the second OGTT exceeds 30 mg/dL (empagliflozin will be inferior). Secondary endpoints comprise the average change in insulin secretory capacity and insulin sensitivity, derived from the first to the second OGTT, the average change in HbA1c at 3 months and at 1 year, compared to baseline, changes in body weight, fluid overload (determined by bioimpedance spectroscopy) and blood pressure. Safety endpoints include clinically concerning hyperglycemia after discontinuation of exogenous insulin, ketoacidosis, urinary tract infections and genital infections, worsening of renal function, hypoglycemia, hospitalizations, cardiovascular events and death. The effect of empagliflozin on the renin-angiotensin system is part of an OeNB-funded project in non-transplanted patients and will be included in the analyses of the present study.