Inclusion Criteria:  Patients with type 2 diabetes mellitus and an indication for metformin according to the American Diabetes Association (American Diabetes Association, 2021a) starting a new metformin treatment. The main marker will be fasting plasma glucose levels of 7.0mmol/L and/or HbA1c 6.5% (American Diabetes Association, 2021a). Written informed consent.  Exclusion Criteria:  Patients under 18 years of age. Clinically significant concomitant disease (e.g. advanced renal failure, hepatic dysfunction, neoplasia). Significant musculoskeletal disease. Active infection during sample collection. Immunosuppressive medical therapy. Hormonal/steroid treatment. Pregnancy. Psychiatric disease and known social behavior altering medication (e.g. antipsychotic medication). Known or suspected malcompliance, drug or alcohol abuse. Inability to follow the procedures of the study, e.g. due to insufficient language skills, severe dementia. Life-expectancy < 6 months. Poor tolerability to metformin treatment with following treatment discontinuation within duration of follow up.