BackgroundT1D treatment requires informed self-responsible patients, who, however, frequently miss their therapeutic goals, providing considerable potential for improvement.MethodsThis observational report evaluates T1D patients [N = 109], aged ≥18 years (range 22–82), poorly controlled at home, at and 3 weeks after their admission to our diabetes rehabilitation clinic [DRC], where they were offered standardized, but unmonitored life-style modification.ResultsAt admission, patients displayed elevated HbA1c values (66 mmol/mol [57; 81]), a high prevalence of co-morbidities (88%), lipodystrophies due to monolocal insulin injections (42%), a low rate of influenza (16%) and pneumococcal (7%) immunization, and underuse of lipid-lowering drugs (-38%). Standardization of life-style improved glucose (p<0.0001) and lipid metabolism (LDL/HDL ratio p<0.01) permitting reduction of insulin dose and reduction of add-on glucose-lowering drugs (GLDs) other than metformin. Outcome was independent of the mode of insulin treatment strategy and more marked at initially high HbA1c, with DRC-costs/d less than 25% of those encountered at standard hospitals.ConclusionType 1 diabetes care requires i) insulin treatment, food intake and life style to be handled in concert, ii) this need cannot be replaced by arbitrary addition of add-on GLDs, and iii) training to this end is 75% cheaper at a DRC than in standard hospitals.