Metformin for type 2 diabetes

Metformin is the medicine that most people with type 2 diabetes start taking when diet and exercise have not been enough to reduce raised blood glucose levels.

It can be used alone, or combined with other diabetes medicines, including insulin, to control blood glucose levels.

Metformin (the active ingredient in the medicine that makes it work) is available as many different brands (e.g. Diabex XR, Diaformin XR, Formet, Glucophage, Metex XR).

See our complete list of all the brands of metformin available in Australia.

Note about medicine names

Most medicines have two names: the active ingredient and the brand name. The active ingredient is the chemical in the medicine that makes it work. The brand name is the name given to the medicine by its manufacturer. There may be several brands that contain the same active ingredient. This website uses active ingredient names, with brand names in brackets. We also discuss medicines in groups or ‘classes’, when their effects or actions are very similar.

To find out more about active ingredients and brand names look at our Brand choices information.

What does metformin do?

Metformin lowers blood glucose by reducing the amount of glucose that the liver releases into the bloodstream, and by increasing the amount of glucose that is taken up into the cells of the body.

What are the benefits of taking metformin?

Metformin is commonly prescribed for diabetes. Its benefits and side effects have been observed for many years and are well understood, unlike newer medicines. Metformin has been shown to reduce the complications of diabetes, a very important benefit of this medicine.


  • is very unlikely to cause abnormally low blood glucose levels or ‘hypos’ (hypoglycaemia)
  • does not cause weight gain and may help weight loss, so it is particularly suitable for people who are overweight
  • reduces ‘bad cholesterol’ (low-density lipoprotein [LDL]) and triglycerides (another kind of fat in the blood).

Who is metformin for?

  • People with type 2 diabetes
  • Adults, and children older than 10 years, especially those who are overweight.

You may not be able to take metformin if you have moderate or severe kidney disease, liver problems, or heart failure — or you may need to take a lower dose.

What are the side effects of metformin?

Common side effects of metformin include:

  • diarrhoea
  • feeling sick (nausea)
  • being sick (vomiting)
  • stomach upset, cramps and bloating (gastrointestinal side effects).

Up to three in 10 people (20% to 30%) taking metformin will experience these gastrointestinal side effects. The side effects can depend how much you are taking (worse side effects occur with larger doses).

Increasing the dose slowly over time to the required dosage and taking metformin with food helps to minimise gastrointestinal side effects.

Who can I ask about side effects?

If you’re concerned that you or someone in your care may have had side effects related to a medicine, seek medical advice. People with questions about their medicines or seeking general information about side effects can also call the NPS Medicines Line on 1300 633 424 (Monday-Friday, 9am-5pm). To report possible side effects call the Adverse Medicine Events (AME) line on 1300 134 237 from anywhere in Australia (Monday–Friday, 9am–5pm AEST).


It is important to tell your health professional about all the medicines you are taking — including prescription, over-the-counter and complementary medicines (herbal, ‘natural’, vitamins and minerals) — as they may interact with diabetes medicines and affect your blood glucose levels. This may mean that your doctor will need to adjust your dose of metformin, or make changes to your other medicines.

Some medicines are known to affect blood glucose levels. Click on the following links to view tables that list some of these medicines:

Apart from these, other medicines that may interact with metformin include:*

  • cimetidine — used to treat ulcers and reflux of stomach acid or gastric reflux
  • topiramate — used to treat migraine and epilepsy.

*As there are often many different brands of one medicine, we have only listed the active ingredients of the medicines here. To find out more, read our information about active ingredients and brand names.

Phone for medicines information

Call Medicines Line on 1300 MEDICINE (1300 633 424) to get information about your prescription, over-the-counter and complementary medicines (herbal, 'natural', vitamins and mineral supplements) from a pharmacist. Your call will be answered by healthdirect Australia (except Queensland and Victoria).