Metformin: The Over‑30 Metabolic Medicine Every Australian Should Know About

A doctor’s review for patients who are tired, gaining weight, worried about sugar, and ready to take control.

Attention — Are you over 30 and fighting your own body?

You wake up tired. You crave sugar and carbs. Your weight creeps up even though you eat less than you used to. Your blood test shows “borderline” sugar, fatty liver, or cholesterol that keeps rising. Maybe your memory is not as sharp, or you have polycystic ovary syndrome and irregular periods. Perhaps you watch a parent with type 2 diabetes and silently fear the same road: daily needles, damaged eyes, numb feet, failing kidneys, even dementia.

Here is the good news: one medicine has been used safely for more than 60 years, costs very little on the PBS, and tackles many of these problems at the root. That medicine is metformin.

Interest — Meet metformin: the most trusted glucose medicine in Australia

As an Australian GP, I prescribe metformin more than almost any other diabetes medicine. It is not a new fad. It comes from the French lilac plant, it is on the World Health Organization’s List of Essential Medicines, and it is the first-line treatment for type 2 diabetes in every major Australian guideline.

Metformin does three powerful things:

• Reduces the amount of glucose your liver dumps into your bloodstream — especially overnight.
• Improves your body’s sensitivity to insulin, so your muscles use sugar more efficiently.
• Helps control appetite and can support modest weight loss in many people.

Desire — Your real-world questions answered without the fear

Many patients hesitate because of old warnings, internet myths, or a friend’s story about side effects. Let me give you the clinical truth on the eight questions I hear most often.

1. Is there a link between metformin and dementia?

This is a huge concern for people over 30 who have watched dementia affect their parents. The short answer: metformin does not cause dementia. In fact, several large observational studies in people with diabetes have found that metformin users may have a lower risk of developing dementia compared with those on other glucose medicines. The important caveat is vitamin B12. Long-term metformin can reduce B12 absorption, and low B12 can cause memory problems and nerve symptoms. That is why a good GP will monitor your B12 level and, if needed, prescribe oral B12 supplements. Bottom line: metformin is not a dementia risk; it may even be protective, but monitor B12.

2. What is the risk of lactic acidosis with metformin?

Lactic acidosis is the side effect that scares many patients because older information overstated it. In reality, the risk is extremely rare — roughly 3 to 10 cases per 100,000 patient-years. By comparison, untreated type 2 diabetes causes heart attacks, kidney failure, blindness, and amputations every single day. The people at risk are those with severe kidney impairment, severe liver disease, uncontrolled heart failure, severe dehydration, or heavy alcohol intake. That is why your GP checks your kidney function before and during treatment. If your eGFR is above 30 mL/min/1.73m² and you are not severely unwell, metformin is very safe. Bottom line: fear of lactic acidosis should not stop you from taking metformin if you have no major kidney or liver disease.

3. Metformin for non-alcoholic fatty liver disease (NAFLD)?

Fatty liver is now one of the most common liver problems in Australia, especially in people over 30 who carry excess weight around the middle. Metformin is not a dedicated liver-repair drug, but it improves the insulin resistance that drives fat accumulation in the liver. Studies show metformin can reduce ALT liver enzymes and improve metabolic features of NAFLD. However, it is not a standalone cure — weight loss remains the strongest treatment. Bottom line: if you have fatty liver and insulin resistance, metformin can be a helpful partner, not a miracle pill.

4. Does metformin cause diarrhea?

Yes, this is the most common side effect, especially in the first weeks. Up to 20–30% of people experience loose bowel motions, bloating, or nausea. But here is the key: it usually settles within days to weeks, and there are simple ways to reduce it:

• Start with a low dose: 500 mg once daily with the evening meal.
• Take it with food, never on an empty stomach.
• Increase the dose slowly, every 1–2 weeks.
• Ask your GP about the extended-release formulation, which is gentler on the gut.

Bottom line: diarrhea is inconvenient but manageable; do not give up before trying the slow-start method or extended-release version.

5. Does metformin interact with statins?

Many Australians over 30 take a statin for high cholesterol. The good news: metformin and statins can be taken together safely. There is no meaningful drug-drug interaction that raises statin levels or increases muscle damage. Some people experience stomach upset from either medicine, but taking them at different times of day can help. If you get muscle pain on a statin, that is usually a statin-specific issue, not a metformin interaction. Bottom line: the combination is common, safe, and often complementary.

6. What is the evidence for metformin in aging?

This is one of the most exciting areas of research. Metformin influences pathways that govern cellular energy and inflammation — including AMPK and mTOR — which are linked to aging and age-related diseases. Observational studies suggest people with diabetes taking metformin may have lower rates of cardiovascular disease, certain cancers, and overall mortality compared with non-users. The TAME trial is now testing metformin specifically for age-related conditions. However, metformin is not yet approved in Australia as an anti-aging drug. Bottom line: if you have metabolic risk factors, metformin may give you broad health benefits that look like “anti-aging,” but do not take it for aging alone without a medical reason.

7. Metformin for ovulation induction?

For women with polycystic ovary syndrome who have irregular cycles and difficulty conceiving, metformin can be a game-changer. It reduces insulin levels, which in turn lowers androgen hormones and may restore normal ovulation. It is often used alone or with clomiphene or letrozole. Pregnancy rates improve in some women, particularly those with insulin resistance. Bottom line: if irregular periods and metabolic issues are in your picture, ask your GP or fertility specialist whether metformin fits your plan.

8. Does metformin affect urine colour?

Metformin itself does not turn urine a different colour. However, if you develop diarrhea or vomiting and become dehydrated, your urine may become dark and concentrated. More importantly, if you ever have dark urine plus severe muscle pain, severe weakness, or fast breathing, stop metformin and seek urgent medical attention — this is a warning sign, not for ordinary use. Bottom line: metformin does not stain urine; dark urine usually means dehydration or another problem.

Action — Take control before your next blood test

You do not need to wait until diabetes is fully established. If you are over 30 and recognise yourself in any of these patterns — rising fasting glucose, fatty liver, PCOS, stubborn weight around the middle, metabolic syndrome — then a conversation with your GP about metformin could be one of the most important steps you take this year.

Ask your doctor to check your HbA1c, fasting glucose, kidney function, liver function, and vitamin B12. If metformin is right for you, your GP can prescribe it on the PBS, and you can fill your script at any Australian pharmacy. It is inexpensive, widely available, and supported by decades of real-world safety.

Book a GP appointment this week. Ask: “Could metformin help my blood sugar, weight, liver, or ovulation?”

This article is general medical information from a doctor’s perspective for Australian readers. It is not individual medical advice. Always consult your GP before starting, stopping, or changing any medicine.