Select language:
On this page

    Last updated: September 2023


    Prescription under medical supervision

    Therapeutic action

    • Biguanide antidiabetic 


    • First-line treatment of type 2 diabetes, when diet and lifestyle measures alone are insufficient, as monotherapy or in combination with another antidiabetic 

    Forms and strengths

    • 500 mg and 1 g tablets

    Dosage and duration

    • Adult: 
      • Week 1: 500 mg once daily in the morning
      • Week 2: 500 mg 2 times daily (morning and evening)

    Increase if necessary in increments of 500 mg per week, according to blood glucose levels and as long as the drug is well tolerated, without exceeding 2 g daily (1 g morning and evening). 

    Contra-indications, adverse effects, precautions

    • Do not administer to patients with: ketoacidosis; cardiac, respiratory, hepatic or severe renal impairment.
    • May cause:
      • often: dose-related gastrointestinal disturbances (nausea, vomiting, diarrhoea, abdominal pain), loss of appetite, metallic taste in mouth;
      • rarely: lactic acidosis (in the event of acute alcohol intoxication, dehydration, taking drugs that alter renal function, etc.); decreased absorption of vitamin B12 (risk of macrocytic anaemia).
    • Reduce dose (max. 1 g daily) in case of moderate renal impairment.
    • Monitor combination with:
      • diuretics, angiotensin-converting enzyme inhibitors, non-steroidal anti-inflammatory drugs (risk of lactic acidosis due to altered renal function);
      • drugs increasing blood glucose levels: corticosteroids, hydrochlorothiazide, salbutamol, chlorpromazine.
    • Stop metformin before surgery or the injection of iodinated contrast agents. Resume treatment 48 hours later after checking renal function.
    • Pregnancy: insulin is the drug of choice for type 2 diabetes in pregnant women (improved glycaemic control; reduced risk of foetal anomalies and neonatal complications). Nevertheless, metformin is not contra-indicated.
    • Breast-feeding: no contra-indication


    • To reduce gastrointestinal intolerance, gradually increase the dose and take tablets with meals. 


    –  Below 25 °C