Metformin therapy in patients with chronic kidney disease

Metformin therapy is limited in patients with chronic kidney disease (CKD) due to the potential risk of lactic acidosis. This open‐label observational study investigated metformin and lactate concentrations in patients with CKD (n = 22; creatinine clearances 15–40 ml/min) and in two dialysed patients. Patients were prescribed a range of metformin doses (250–2000 mg daily) and metformin concentrations were compared with data from healthy subjects (scaled to 1500 mg twice daily). A subset of patients (n = 7) was controlled on low doses of metformin (250 or 500 mg daily). No correlation between metformin and lactate concentrations was observed. Three patients had high lactate concentrations (>2.7 mmol/l) and two had high metformin concentrations (3–5 mg/l), but none had any symptoms of lactic acidosis. Reducing metformin dosage and monitoring metformin concentrations will allow the safe use of metformin in CKD, provided that renal function is stable.