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What does it do?

Metformin is used to treat diabetes, and sometimes other conditions.

How should you take it?

Take metformin regularly as directed with food and a glass of water.

What if you forget a dose?

Take the missed dose as soon as possible (with food). If it is close to the time for your next dose, skip the missed dose and carry on as normal. Do not take two doses at the same time.

Can you take other medicines?

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins, herbal products or recreational drugs.

What side effects might you notice?

Side EffectsRecommended action

Severe vomiting or diarrhoea

Stop taking and tell your doctor

Weakness, headache

Changes in taste, change of appetite

Stomach upset, farting, indigestion

Tell your doctor if troublesome

If you notice any other effects, discuss them with your doctor or pharmacist.

Other information:

  • Very rarely, metformin can cause a serious condition called lactic acidosis. Stop taking metformin and tell your doctor immediately if you are feeling very unwell or unusually tired, or if your breathing becomes faster than normal.
  • Tell your doctor if you have kidney, liver or heart problems.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
  • Test your blood sugar as directed by your health professional.
  • Limit alcohol intake as it may change your blood sugar and increase your risk of metformin side effects.

This leaflet contains important, but not all, information about this medicine.

Prepared by the PILs Committee at Christchurch Hospital, Canterbury District Health Board, New Zealand. April 2016

For more general information about this sheet and its contents, see: What does a My Medicines sheet cover?

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About My Medicines

My Medicines Patient Information Leaflets (PILs) contain important, but not all, information about the medicines they describe.

For more information about the sheets, see: What does a My Medicines sheet cover?

My Medicines is developed by a team at the Canterbury District Health Board. Our team is made up of doctors, pharmacists, and a non-medical person to help us keep to plain language. We also discuss our information with specialist health professionals or groups when needed