Metformin in Australia: A Doctor’s Review of the Tried-and-True Diabetes Defender

By an Australian general practitioner

Attention: The Silent Threat of Type 2 Diabetes After 30

If you are over 30 and have been told your blood sugar is high, you are not alone. Type 2 diabetes affects more than 1.3 million Australians, and a huge number of people are living with prediabetes without knowing it. The real danger is not the diagnosis itself — it is what happens when high blood sugar is left unchecked for years: damaged eyes, failing kidneys, numb or burning feet, and a much higher risk of heart attack or stroke.

As a doctor, I see the fear in my patients’ eyes when we talk about diabetes complications. Many people worry they will end up on insulin, gain weight, or lose their independence as they age. The good news is that one medicine has stood the test of time for decades, is available in every Australian pharmacy, and costs far less than most newer diabetes drugs. That medicine is metformin.

This review will explain what metformin really does, what it can and cannot do, and why it remains the first-choice treatment for type 2 diabetes in Australia. If you are looking for a safe, effective, affordable way to protect your future, keep reading.

Interest: What Is Metformin and Why Do Australian Doctors Trust It?

Metformin belongs to a class of medicines called biguanides. It lowers blood glucose mainly by reducing the amount of sugar your liver produces and by improving your body’s sensitivity to insulin. Unlike some diabetes medicines, metformin does not cause weight gain when used alone, and it does not cause dangerous low blood sugar (hypoglycaemia) in most patients.

It is not insulin, so there are no daily injections. It comes as a tablet that is taken with meals. In Australia, metformin is listed on the Pharmaceutical Benefits Scheme (PBS), which means it is heavily subsidised and affordable for almost everyone.

Desire: The Evidence That Makes Metformin a Lifelong Ally

Now let me answer the questions I hear most often from patients over 30 — the real concerns behind the “what ifs” of living with diabetes.

Does metformin reduce microvascular complications?

Yes. Microvascular complications are the small-vessel damage that causes blindness, kidney failure and nerve damage in diabetes. The landmark UK Prospective Diabetes Study (UKPDS) showed that improving long-term blood glucose control significantly reduces the risk of retinopathy (eye damage), nephropathy (kidney damage) and neuropathy (nerve damage). Metformin lowers HbA1c effectively and sustainably without causing weight gain, which makes it a powerful tool for protecting your small blood vessels over time.

In overweight people with type 2 diabetes, metformin reduced overall diabetes-related endpoints and mortality. By keeping glucose levels steadier year after year, metformin helps protect your eyes, kidneys and nerves from the silent damage of high blood sugar.

What is the effect of metformin on appetite hormones?

Many people over 30 struggle with constant hunger, cravings and weight gain. Metformin has a subtle but useful effect on appetite hormones. It increases hormones called GLP-1 and peptide YY (PYY), which signal fullness to your brain. It may also reduce ghrelin, often called the “hunger hormone.”

The practical result is that many patients feel less hungry, eat smaller portions, and find it easier to avoid weight gain — or even lose a few kilograms. This is a major advantage, because many other diabetes medicines, including insulin and some sulfonylureas, tend to cause weight gain. Metformin works with your body instead of against it.

Can metformin be used in elderly patients?

Yes, with sensible precautions. Older Australians can use metformin safely, but kidney function must be checked regularly. Your doctor will measure your eGFR (estimated glomerular filtration rate). In general:

• If eGFR is above 45 mL/min/1.73m², metformin can usually be used normally.
• If eGFR is between 30 and 45, your doctor may reduce the dose and monitor more closely.
• If eGFR is below 30, metformin should be avoided because of the rare but serious risk of lactic acidosis.

This may sound technical, but the message is simple: metformin is not automatically stopped just because you get older. With annual blood tests and dose adjustments, many of my older patients continue taking metformin safely for decades.

Does metformin affect thyroid lab tests?

It can. If you take levothyroxine for an underactive thyroid, metformin may lower your TSH level on blood tests without changing your free T4 or free T3 levels. This does not mean your thyroid has suddenly become overactive or that your thyroid disease has worsened. It is a laboratory interaction, not a true change in thyroid function.

Why does this matter? Because if you have thyroid disease and diabetes, your doctor needs to interpret your TSH results carefully to avoid unnecessary changes to your thyroid medication. This is one of the many reasons to always tell your GP about all your medicines, including metformin.

What is the shelf life of metformin tablets?

Most metformin tablets have a shelf life of 2 to 3 years from the date of manufacture, provided they are stored correctly. Keep your metformin in a cool, dry place below 25°C, away from direct sunlight and moisture. Do not store it in the bathroom cabinet, and do not use tablets after the expiry date printed on the blister pack or bottle.

If you find an old packet at the back of the cupboard, check the expiry date before taking it. When in doubt, return expired medicines to your local pharmacy for safe disposal. Buying a 90-day or 6-month supply from your Australian pharmacy is safe and cost-effective, but always store it properly.

Are there any new metformin formulations in development?

Yes. Researchers continue to study metformin even after more than 60 years of use. New approaches include delayed-release metformin that targets the lower gut, aiming to improve glucose control with lower doses and fewer stomach side effects. Fixed-dose combinations of metformin with newer diabetes medicines are also being developed and refined. Some scientists are even investigating metformin’s potential anti-ageing and heart-protective effects, though these are not yet established enough to change prescribing guidelines.

In Australia, extended-release (XR) metformin is already available and can reduce gut upset, making it a good option if standard metformin causes bloating, nausea or diarrhoea.

What is the half-life of metformin?

The plasma half-life of metformin is about 6 hours, which means it leaves the bloodstream relatively quickly. However, its effects on the liver and gut last longer because metformin accumulates inside cells. This is why standard metformin is usually taken two to three times a day with meals, while extended-release metformin is taken once daily. The half-life also explains why it is important to take metformin regularly — skipping doses means your glucose control can slip within a day or two.

Are there generic versions of metformin in Australia?

Absolutely. Metformin has been off-patent for many years, and there are multiple PBS-listed generic versions available in Australia. Common brands include Diaformin, Diabex, Metex, and many others. Generic metformin contains the same active ingredient and is just as effective as the original brand, but it costs much less.

This is one of the biggest advantages of metformin compared with newer diabetes drugs, which can cost hundreds of dollars per month. With metformin, you can often get a month’s supply for a fraction of that price, especially with a concession card. It is one of the most affordable prescription medicines in Australia.

Action: Take the Next Step for Your Health

If you are over 30 and living with type 2 diabetes, prediabetes, polycystic ovary syndrome (PCOS), or struggling with weight and rising blood sugar, metformin could be the safe, effective and affordable first step you need. It has decades of evidence, a strong safety record, and a price that won’t break the bank.

Talk to your Australian GP about whether metformin is right for you. Ask about PBS-subsidised generic metformin, and mention extended-release if you are worried about stomach side effects. Your doctor can check your kidney function, HbA1c and thyroid tests, then give you a prescription that your local pharmacy can fill quickly and affordably.

Do not wait for complications to appear. Every day with high blood sugar does small amounts of damage to your eyes, kidneys and nerves. Metformin is not a miracle cure, but it is one of the best tools we have to protect your future. Book an appointment today, get your blood sugar checked, and take control — your body will thank you for it.