Metformin
- Generic name
- metformin hydrochloride
- Brand names
- Glucophage, Glucophage XR
Medically reviewed by Marcus Bell, PharmDWritten by Priya Nair, MPHUpdated on
What is metformin?
Metformin is a prescription medicine used to lower blood sugar in adults and children with type 2 diabetes. It has been used for decades, is inexpensive and is usually the first medicine recommended, alongside healthy eating and physical activity.
It works mainly by reducing the amount of glucose your liver releases and by helping your body respond better to insulin. On its own, it rarely causes low blood sugar.
What it's used for
- Treating type 2 diabetes in adults and children aged 10 and older
- Sometimes used, off-label, for prediabetes or polycystic ovary syndrome (PCOS) — your doctor will explain whether it's right for you
Forms and strengths
| Form | Available strengths |
|---|---|
| Immediate-release tablet | 500 mg, 850 mg, 1,000 mg |
| Extended-release tablet | 500 mg, 750 mg, 1,000 mg |
| Oral solution | 500 mg per 5 mL |
Your prescriber decides which form and dose is right for you.
Side effects
Common side effects
- Diarrhoea
- Nausea or upset stomach
- Gas and bloating
- Metallic taste
- Reduced appetite
Tell your doctor if these are severe or don't go away.
Serious side effects
- Lactic acidosis (rare): unusual muscle pain, trouble breathing, stomach pain, feeling very weak or cold — get emergency help
- Low vitamin B12 levels with long-term use
- Low blood sugar when combined with insulin or sulfonylureas
Call your doctor right away, or emergency services if symptoms are life-threatening.
Interactions
Tell your prescriber and pharmacist about all medicines and supplements you take. Important interactions include:
- Iodinated contrast dye used for some scans — metformin may need to be paused
- Alcohol — heavy drinking increases the risk of lactic acidosis
- Other diabetes medicines such as insulin or sulfonylureas — may increase the risk of low blood sugar
- Some medicines that affect the kidneys
Warnings
- Metformin isn't suitable for people with severe kidney problems; your doctor will check your kidney function before and during treatment.
- It may need to be stopped temporarily before surgery, during severe illness or dehydration, or before some imaging tests.
- Taking it with meals and starting at a low dose helps reduce stomach side effects.
Follow your prescriber's instructions for how much to take and when. Don't start, stop or change your dose without talking to them.
Cost and alternatives
Metformin is available as a low-cost generic. Alternatives or add-on treatments include SGLT2 inhibitors, GLP-1 receptor agonists, DPP-4 inhibitors, sulfonylureas and insulin. The right choice depends on your health, other conditions and preferences.
Frequently asked questions
Does metformin cause weight gain?
No. Metformin is generally weight-neutral and some people lose a small amount of weight while taking it.
Should I take metformin with food?
It's usually taken with meals to reduce stomach upset, but follow the instructions from your prescriber or pharmacist.
How we reviewed this article
Beargoal has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions and medical associations. We avoid tertiary references. Learn more in our editorial process.
- MedlinePlus Metformin. U.S. National Library of Medicine. https://medlineplus.gov/druginfo/meds/a696005.html
- American Diabetes Association Professional Practice Committee (2024). 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Care in Diabetes—2024. Diabetes Care. https://diabetesjournals.org/care/issue/47/Supplement_1
- October 7, 2026Reviewed by a clinical pharmacist and published. Medically reviewed by Marcus Bell, PharmD.
Medically reviewed by Marcus Bell, PharmDWritten by Priya Nair, MPHUpdated on
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