Metformin: The Underestimated Guardian of Your Metabolic Health

Written from a doctor’s perspective for Australians aged 30 and over.

Attention: Why You Should Care About Metformin Right Now

If you are over 30, you may have noticed things changing. Your waistline is slowly expanding, your energy crashes mid-afternoon, you crave sugar more often, and your doctor has mentioned words like “insulin resistance”, “borderline blood sugar”, “fatty liver”, or maybe you have been living with polycystic ovary syndrome (PCOS) for years without real answers. Perhaps you are frightened of needles, insulin, or expensive new medicines. Maybe you have watched a parent struggle with type 2 diabetes, kidney disease, or heart problems and you want to avoid the same path.

What if I told you that one medicine has been used for more than 60 years, is listed on the PBS, costs very little, and can help address many of these problems at the same time? That medicine is metformin.

In my practice, metformin is one of the most prescribed medicines — not because it is fashionable, but because it is effective, generally well tolerated, and backed by decades of Australian and international evidence. In this review, I will explain what metformin is, what it can do for you beyond just lowering glucose, and how to manage common concerns such as itching, vitamin B12 deficiency, kidney stones, abdominal pain, and more.

Interest: What Is Metformin and How Does It Work?

Metformin belongs to a class of medicines called biguanides. It works mainly by:

• Reducing the amount of glucose your liver produces, especially overnight.
• Improving your body’s sensitivity to insulin in muscles, so glucose can be used for energy instead of staying in the bloodstream.
• Modestly reducing the absorption of glucose from the gut.

Unlike many other diabetes medicines, metformin does not cause hypoglycaemia (dangerously low blood sugar) when used alone. It is weight neutral or can even support modest weight loss in many people. This matters enormously because weight gain is a common and distressing side effect of many diabetes and PCOS medicines.

Metformin is TGA-approved in Australia for type 2 diabetes. It is also widely used off-label for PCOS and is being studied in non-alcoholic fatty liver disease (NAFLD). It is taken by mouth, usually once or twice daily with meals, which makes it very practical for busy adults.

Desire: The Benefits That Go Far Beyond Blood Sugar

Many people think of metformin only as a “diabetes pill”. But as a doctor, I see its value extending much further. Here is a table summarising the key benefits that matter to Australian adults over 30:

What are the benefits of metformin beyond glucose lowering?

Beyond glucose control, metformin helps address the underlying insulin resistance that drives many modern metabolic conditions. It can improve ovulation in PCOS, reduce liver fat in NAFLD, modestly support weight loss, and lower cardiovascular risk in people with type 2 diabetes. Some long-term studies also suggest a possible reduction in certain cancers and improvement in overall survival in people with diabetes, although more research is ongoing. For Australians over 30, this means metformin is not just a sugar-lowering tablet — it is a metabolic health tool.

Can metformin cause kidney stones?

This is a common fear, but the answer is reassuring: metformin is not known to cause kidney stones. The confusion arises because metformin is excreted by the kidneys, and its use must be adjusted or avoided when kidney function is significantly reduced. However, metformin does not form stones in the urinary tract. In fact, some observational studies suggest metformin may be associated with a lower risk of kidney stones compared with some other diabetes medicines, possibly because it improves insulin resistance and lowers uric acid levels in some people. If you have a history of kidney stones, metformin is generally safe to use provided your kidney function is monitored. The important point is to check your kidney function (eGFR) before and during treatment.

RACGP guideline for metformin initiation?

The Royal Australian College of General Practitioners (RACGP) and Diabetes Australia recommend metformin as first-line therapy for most people with newly diagnosed type 2 diabetes, unless there is a contraindication or it is not tolerated. The usual starting approach in Australia is:

• Start with 500 mg once daily with the evening meal or breakfast.
• Increase by 500 mg every 1–2 weeks as tolerated, up to 2000 mg per day in divided doses.
• Use the lowest effective dose and always take with food to reduce stomach upset.
• Check kidney function before starting and at least yearly, more often in older adults or those with kidney concerns.
• Do not use if eGFR is below 30 mL/min/1.73 m²; use with caution and dose adjustment if eGFR is 30–45.

Many GPs also consider metformin for adults with prediabetes who are at high risk, especially if they are under 60, overweight, or have a history of gestational diabetes. This is not universal but is used in selected cases.

What is the evidence for metformin in NAFLD in Australian adults?

Non-alcoholic fatty liver disease (NAFLD) is now very common in Australia, affecting an estimated 1 in 3 adults. Metformin is not specifically TGA-approved for NAFLD, but it is often used in people with diabetes and fatty liver because it improves insulin resistance and may lower liver enzymes (ALT). Australian and international studies show that metformin can reduce liver fat and improve liver inflammation in some people, although it is not considered the strongest medicine for advanced NASH. The foundation of NAFLD treatment remains weight loss, diet, and exercise, but metformin can be a useful partner, especially if you have prediabetes or type 2 diabetes.

Is metformin used in polycystic ovary syndrome (PCOS) in Australia?

Yes. In Australia, metformin is commonly used off-label for PCOS, particularly in women who have insulin resistance, irregular periods, difficulty losing weight, or metabolic risk factors. It can help:

• Improve menstrual cycle regularity.
• Support ovulation in some women.
• Reduce insulin and androgen levels.
• Improve metabolic markers such as cholesterol and blood pressure.

For fertility specifically, medicines such as letrozole are often considered first-line, but metformin may be added, especially if there is glucose intolerance or obesity. If you have PCOS and are planning a pregnancy, speak with your GP or endocrinologist about whether metformin is right for you.

Can metformin cause itching?

Itching is not a common side effect of metformin, but it can rarely occur as part of an allergic skin reaction. In clinical practice, most itching reported by patients taking metformin turns out to be unrelated — dry skin, eczema, or another medicine. However, if you develop a new rash, hives, or widespread itching shortly after starting metformin, you should stop the medicine and contact your doctor. If itching is accompanied by swelling of the face, lips, or tongue, or difficulty breathing, call 000 immediately. For most people, metformin does not cause itching, and this concern should not prevent you from trying it.

Metformin and vitamin B12 deficiency: prevention?

Long-term use of metformin can reduce the absorption of vitamin B12 in the gut. This is a well-known effect and can lead to low B12 levels, which may cause fatigue, tingling or numbness in the hands and feet, memory problems, and anaemia. The good news is that this is preventable and manageable.

Prevention strategy in Australia:

• Check vitamin B12 levels before starting metformin or within the first year, then at least every 1–2 years, especially if you are on metformin long-term.
• If B12 is low or borderline, your doctor may recommend oral vitamin B12 supplements or B12 injections.
• Do not stop metformin simply because of B12 concerns — the deficiency can be corrected while continuing metformin.

For Australians over 30, particularly vegetarians, vegans, older adults, or those on stomach acid medicines, B12 monitoring is especially important.

What to do if metformin causes severe abdominal pain?

This is a critical question. Mild stomach upset, nausea, or diarrhoea is common when starting metformin and often settles. However, severe abdominal pain is different and should never be ignored. Here is what you need to know:

Lactic acidosis is extremely rare and usually only occurs in people with severe kidney impairment, severe dehydration, heavy alcohol intake, or serious illness. But because it is serious, we treat severe abdominal pain with caution. Never push through severe pain — stop the medicine and get help.

Action: Your Next Steps to Better Metabolic Health

If you are over 30 and struggling with any of the following, metformin may be worth discussing with your GP:

• Type 2 diabetes or prediabetes.
• Difficulty losing weight despite diet and exercise.
• Polycystic ovary syndrome (PCOS) with irregular periods or insulin resistance.
• Fatty liver disease diagnosed on ultrasound or blood tests.
• A strong family history of type 2 diabetes or heart disease.
• Fear of needles, insulin, or weight gain from other medicines.

Metformin is a PBS-subsidised medicine in Australia, meaning you can obtain it at any Australian pharmacy with a valid prescription from your doctor. It is one of the most affordable, evidence-based medicines available for metabolic health. Ask your GP for a metabolic health review today.

Take control of your health now. Talk to your doctor about whether metformin is right for you, and if it is prescribed, you can buy it from your local pharmacy knowing you are using a medicine with over six decades of real-world safety and benefit. Your future self will thank you.

Disclaimer: This article is for general educational purposes only and is not a substitute for individual medical advice. Always consult a qualified Australian healthcare professional before starting, stopping, or changing any medicine.