Metnil

What It Is Used For

Metformin lowers blood sugar in type 2 diabetes. It is usually the first medicine used, together with diet and exercise. Doctors also use it for some women with polycystic ovary syndrome (PCOS).

How to Take It

Take it with or just after meals to reduce stomach upset. The doctor usually starts with 500 mg once or twice a day and increases slowly. The usual maximum is about 2 g to 2.5 g a day, split between meals. Extended-release tablets are taken once a day with the evening meal and must be swallowed whole.

Who Should Not Take It

Do not take it if you have severe kidney disease, diabetic ketoacidosis, a severe infection, severe dehydration or shock, serious liver disease, or if you drink large amounts of alcohol.

Side Effects

Common, especially at the start: nausea, diarrhoea, stomach ache, loss of appetite and a metallic taste. These usually settle. Long-term use can lower vitamin B12. A rare but serious side effect is lactic acidosis: get urgent help for severe weakness, fast breathing, muscle pain, stomach pain or feeling very cold.

Precautions

Your kidney function should be checked regularly. Your doctor may ask you to stop it for a short time before surgery or an X-ray scan with contrast dye, and during vomiting, diarrhoea or dehydration. On its own it rarely causes low blood sugar.

Pregnancy and Breastfeeding

It is sometimes used in pregnancy under a doctor's care. Do not start or stop it on your own.

Interactions

Tell your doctor if you take other diabetes medicines, diuretics (water tablets), steroids, or blood pressure medicines. Alcohol increases the risk of lactic acidosis.

Storage

Store below 30°C in a dry place, out of the reach of children.