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Metformin in Australia: Why GPs Still Trust This Proven Diabetes Medicine First
Written from the perspective of a practising Australian GP
Attention: Are you tired of diabetes medicines that cause weight gain, hypos, or confusion about kidney safety?
If you are over 30 and living with type 2 diabetes, prediabetes, polycystic ovary syndrome (PCOS), or carrying excess weight around your middle, you may feel frustrated. You might worry about needles, weight gain, low blood sugar, kidney damage, or whether a medicine is safe for your long-term health. Perhaps you have heard conflicting advice about metformin and wonder whether it is still relevant today.
As an Australian doctor, I want to give you clear, practical information about metformin — a medicine that has been used for more than 60 years and is still the first-choice tablet for type 2 diabetes in Australia. It is affordable, effective, and, when used correctly, one of the safest diabetes medicines available.
Interest: What makes metformin the cornerstone of Australian diabetes care?
Metformin belongs to a class of medicines called biguanides. It works mainly by reducing the amount of glucose your liver produces and by helping your body respond better to its own insulin. Unlike some other diabetes drugs, metformin does not cause weight gain and rarely causes dangerous low blood sugar when used on its own.
In Australia, the RACGP and Diabetes Australia guidelines recommend metformin as the first-line oral glucose-lowering medicine for type 2 diabetes, alongside healthy eating and regular physical activity. It is listed on the Pharmaceutical Benefits Scheme (PBS), which means most people can access it at a subsidised price.
What is the role of metformin in Australian diabetes guidelines?
Metformin is recommended as the initial medicine for most adults with type 2 diabetes when lifestyle changes alone are not enough to control blood glucose. The Australian diabetes guidelines highlight metformin because it lowers HbA1c effectively, does not cause weight gain, has a low risk of hypoglycaemia, and is affordable. It is also used off-label in some cases of prediabetes and PCOS, but this should always be discussed with your GP or specialist.
Metformin and kidney function: what eGFR is safe?
Many people over 30 worry about their kidneys. The key test is the eGFR, which measures how well your kidneys are filtering blood. The table below summarises how Australian doctors approach metformin use based on eGFR.
| eGFR (mL/min/1.73 m²) | What Australian doctors usually consider |
|---|---|
| Above 60 | Safe for standard metformin use; routine kidney monitoring advised. |
| 45–60 | Safe to continue metformin; check kidney function every 6–12 months. |
| 30–45 | Use with caution, often at a reduced dose; monitor eGFR every 3–6 months and avoid dehydration. |
| Below 30 | Metformin should usually be stopped or avoided due to increased risk of lactic acidosis. |
If you have kidney concerns, do not stop metformin yourself. Speak with your GP, who can adjust the dose safely.
Metformin for type 2 diabetes in Aboriginal and Torres Strait Islander peoples
Type 2 diabetes occurs at higher rates and often at a younger age in Aboriginal and Torres Strait Islander communities. Metformin is a first-line treatment in these communities because it is effective, affordable, and does not cause hypoglycaemia when used alone. It can be used safely with lifestyle programs and culturally appropriate care. Regular kidney and blood glucose checks remain essential, as with all Australians. If you or a family member are Aboriginal or Torres Strait Islander and living with type 2 diabetes, ask your GP or Aboriginal Health Worker about starting metformin early.
Desire: How metformin can address your real-life concerns
How does metformin help with weight management?
Many people over 30 struggle with weight gain, especially if they have been on certain diabetes medicines. Metformin is not a fad weight-loss pill, but it is weight-neutral or can help with modest weight loss — typically around 1 to 3 kg in the first year. It improves insulin sensitivity, which can reduce cravings and help your body store less fat. This makes metformin especially attractive if you have gained weight on other medicines or want to avoid doing so.
How does metformin affect fertility?
This is a common question, particularly for women with PCOS or type 2 diabetes who are trying to conceive. Metformin is not a fertility drug, but by lowering insulin levels, it can improve ovulation in some women with insulin-resistant PCOS. This may help regulate periods and support natural conception. It also improves blood glucose control before pregnancy, which reduces the risk of complications for both mother and baby. If you are planning a pregnancy, always discuss preconception planning with your GP or specialist — metformin may be part of that conversation.
What are the side effects of metformin?
No medicine is perfect, but metformin's side effects are usually manageable. The most common ones occur when starting treatment or increasing the dose.
| Side effect | How common | What you can do |
|---|---|---|
| Nausea, bloating, diarrhoea | Common at first | Take with or after food, start low, increase slowly; often settles within 1–2 weeks. |
| Metallic taste | Uncommon | Usually temporary; sip water or use sugar-free mints. |
| Vitamin B12 deficiency | Can occur long term | Check B12 every 1–2 years; supplement if low. |
| Lactic acidosis | Very rare | Avoid if eGFR below 30; seek urgent help for severe muscle pain, trouble breathing, or extreme weakness. |
Can metformin cause drowsiness?
Metformin alone rarely causes hypoglycaemia, so drowsiness from low blood glucose is uncommon. However, if you take metformin with a sulfonylurea or insulin, low blood sugar can occur and may cause tiredness, confusion, sweating, or drowsiness. Persistent fatigue can also be a sign of vitamin B12 deficiency, which long-term metformin use can sometimes trigger. If you feel unusually sleepy after starting metformin, do not ignore it — speak with your GP. In most cases, the cause can be identified and fixed without stopping metformin.
How to switch from another diabetes drug to metformin?
Switching diabetes medicines should always be done with your GP’s guidance. Never stop insulin or certain tablets suddenly. The process usually involves starting metformin at a low dose and gradually adjusting the other medicine.
| Current medicine | How your GP may switch you |
|---|---|
| Sulfonylurea (e.g. gliclazide, glimepiride) | Start low-dose metformin while gradually reducing sulfonylurea; monitor blood glucose to avoid hypos. |
| DPP-4 inhibitor (e.g. sitagliptin, linagliptin) | Usually stop DPP-4 and start metformin with food; no washout period needed. |
| SGLT2 inhibitor (e.g. dapagliflozin, empagliflozin) | Can overlap or stop; metformin may be added first, then SGLT2 stopped if required. |
| Insulin | Never stop insulin suddenly. Metformin is added and insulin dose adjusted gradually under close supervision. |
In my practice, I usually start metformin at 500 mg once daily with the evening meal, then increase by 500 mg every one to two weeks as tolerated. The usual target dose is 1000 mg to 2000 mg per day, but your doctor will tailor this to you.
Action: Talk to your GP about metformin today
If you are over 30 and have type 2 diabetes, prediabetes, PCOS, or you are struggling with weight and insulin resistance, metformin may be a safe, affordable, and effective option for you. It is the most trusted first-line diabetes medicine in Australia for good reason.
Here is what you can do next:
- Book an appointment with your GP and ask: “Is metformin right for me?”
- Bring a list of your current medicines and any recent blood test results, including eGFR and HbA1c.
- Ask about starting at a low dose to reduce stomach upset.
- Ask for a vitamin B12 check if you have been on metformin for more than a year.
- Discuss your weight, fertility, and kidney health concerns openly — these are all part of good diabetes care.
Metformin is available on the PBS, making it one of the most cost-effective diabetes medicines. Used correctly, it can help you take control of your blood glucose without the fear of weight gain or frequent hypos. Take the next step and speak with your GP today.
Disclaimer: This article is general information only and does not replace individual medical advice. Always consult your doctor before starting, stopping, or changing any medicine.
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