From a central registry at the National Board of Health and Welfare in Sweden collect all patients in the city of Malmö prescribed metformin during two years. Glomerular filtration rate (eGFR) was estimated from the CKD-EPI formula (n=5408) and compared to a control material (n=2815) from the same town. All cases of severe lactic acidosis rendering ICU admission were also sought. The study hypothesis is that metformin is prescribed to patients with lower GFR than anticipated with very few cases of lactic acidosis registered.

Inclusion Criteria:

• Patients in the city of Malmö prescribed metformin at least three times during two years
• Available at least one p-creatinine during the two years

Exclusion Criteria:

All patients irrespective of age prescribed metformin according to a registry for the city of Malmö