M-Form 850 mg Tablet

First-line medicine for type 2 diabetes:

• Type 2 diabetes in adults and children over 10 years, alone or with other diabetes medicines or insulin, together with diet and exercise
• Reduces the risk of diabetes complications in overweight patients
• Polycystic ovary syndrome (PCOS) and prediabetes — on specialist advice

Adults (immediate-release): start 500 mg once or twice daily (or 850 mg once daily) with meals; increase gradually every 1–2 weeks; usual 1.5–2 g daily in 2–3 divided doses; maximum 3 g/day.

Extended-release (XR/SR): start 500 mg once daily with the evening meal; maximum usually 2 g once daily.

Children 10 years and over: start 500 mg once daily; maximum 2 g/day in divided doses.

• Take with or right after meals to reduce stomach upset; swallow XR tablets whole.
• Kidney function (eGFR) decides the maximum dose: reduce if eGFR 30–45; do not use if eGFR below 30.

• Severe kidney impairment (eGFR below 30 ml/min)
• Diabetic ketoacidosis, or conditions causing lactic acidosis: severe infection, shock, dehydration, severe heart or lung failure, recent heart attack
• Severe liver disease, alcohol abuse
• Allergy to metformin

Very common (at the start): nausea, vomiting, diarrhoea, stomach pain, loss of appetite — usually settle in a few weeks.

Common: metallic taste, vitamin B12 deficiency with long-term use.

Rare but serious: lactic acidosis (vomiting, stomach pain, muscle cramps, fast breathing, weakness, feeling very unwell) — needs emergency care. Rare: liver problems, skin reactions.

Metformin alone rarely causes low blood sugar.

• Check kidney function at least yearly (more often in the elderly).
• Stop temporarily during severe vomiting/diarrhoea, dehydration, before surgery and before/after X-ray contrast injections; restart when kidney function is checked.
• Avoid heavy alcohol use.
• Check vitamin B12 if tingling or anaemia develops.

Insulin is usually preferred in pregnancy, but metformin is used in gestational diabetes and PCOS on specialist advice. Small amounts pass into breast milk — generally considered compatible.

• Iodinated contrast media (stop before and for 48 hours after)
• Alcohol (lactic acidosis risk)
• Diuretics, NSAIDs, ACE inhibitors (may affect kidney function)
• Steroids, beta-agonists, thiazides (raise blood sugar)
• Cimetidine, dolutegravir, ranolazine (raise metformin levels)
• Insulin and sulphonylureas (low blood sugar when combined)

Risk of lactic acidosis — emergency treatment, possibly dialysis. Low blood sugar is uncommon.

Store below 30°C, in a dry place.