Metformin — What You Need to Know | KiwiMeds
✅ Reviewed by a Registered Pharmacist NZ | Last updated: May 2026 | This information is for educational purposes and does not replace advice from your doctor or pharmacist.
What is Metformin?
Metformin is one of the most commonly prescribed diabetes medications in New Zealand and worldwide. It belongs to a class of medicines called biguanides and has been used safely for over 60 years. In New Zealand, you may know it by brand names such as Glucophage or simply as “metformin” — the generic version funded by Pharmac.
What is it used for? (NZ context)
Metformin is the first-choice medicine for managing type 2 diabetes in New Zealand. It is fully funded by Pharmac for eligible patients, meaning there is no prescription cost beyond your standard dispensing fee (currently $5 per item, or free for those on a Community Services Card). It is sometimes also used off-label for polycystic ovary syndrome (PCOS) and pre-diabetes.
How does it work?
Unlike some diabetes medications that increase insulin production, metformin works in three ways: it reduces the amount of glucose your liver releases into the bloodstream, it improves the way your body responds to insulin (reduces insulin resistance), and it slightly slows the absorption of glucose from your gut. It does not cause your blood sugar to drop too low on its own, which makes it one of the safer diabetes medicines.
How to take it
Metformin is usually taken with or after food to reduce stomach upset. Your doctor will start you on a low dose and gradually increase it over a few weeks — this helps your body adjust and minimises side effects. Always take it exactly as directed by your doctor or pharmacist. Do not stop taking it without talking to your healthcare provider first.
Common side effects
- Nausea, stomach upset, or diarrhoea — especially when starting or increasing the dose. Taking it with food helps.
- Metallic taste in the mouth
- Loss of appetite (which can actually be helpful for some people with type 2 diabetes)
- These side effects often improve after the first few weeks as your body adjusts
Serious side effects to watch for
Lactic acidosis is a rare but serious side effect. While uncommon, it is important to be aware of symptoms: unusual muscle pain, trouble breathing, unusual sleepiness, stomach discomfort, or feeling cold. If you experience any of these, seek medical attention immediately and tell the doctor you are taking metformin.
Important drug interactions
- Alcohol — drinking heavily while on metformin increases the risk of lactic acidosis. Moderate, occasional drinking is generally fine.
- Contrast dye (used in X-rays/CT scans) — you may need to temporarily stop metformin before and after these procedures. Always tell your doctor or radiographer you take metformin.
- Some blood pressure medications — your doctor will monitor accordingly
Things to avoid while taking it
- Excessive alcohol consumption
- Skipping meals (particularly important if you take other diabetes medicines alongside metformin)
- Stopping the medicine without medical advice
NZ-specific information
Pharmac funding: Metformin is fully funded in New Zealand under the Pharmaceutical Schedule. The generic version (metformin hydrochloride) is what is typically dispensed. Glucophage is a branded version that may not be funded — talk to your pharmacist about what is available.
MEDSAFE approved: Yes. Metformin is approved by Medsafe (New Zealand’s medicine regulator).
Available forms: Tablets (500mg, 850mg) and modified-release tablets (500mg, 750mg, 1000mg).
Frequently asked questions
Can I take metformin if I have kidney problems? Metformin is not recommended if your kidney function is significantly reduced. Your doctor will check your kidney function (eGFR) before prescribing and regularly while you take it.
Will metformin make me lose weight? Metformin is weight-neutral for most people, but some people do lose a small amount of weight due to reduced appetite. It is not prescribed as a weight-loss medicine.
Can I drink alcohol on metformin? Occasional, moderate drinking is generally considered safe. However, heavy or binge drinking is not recommended as it can increase the risk of side effects.
Related medications
If you are reading about metformin, you may also find these medication guides useful: Atorvastatin (cholesterol) | Amlodipine (blood pressure) | Levothyroxine (thyroid)
Always talk to your pharmacist or doctor for personalised advice about your medications. The information on this page is general and educational — it does not replace a consultation with your healthcare provider.
References & Further Information
The following New Zealand and international resources were used to inform this page: