Metformin: A Doctor’s Review of Australia’s Most Underrated Diabetes Medication

Written from a GP’s perspective for people over 30 who want to protect their long-term health.

Attention: The “borderline” blood sugar warning you shouldn’t ignore

If you are over 30, you may have heard any of these from your GP: “Your blood sugar is a little high,” “You have insulin resistance,” or “We need to watch your HbA1c.” Maybe you feel more tired than you used to, carry extra weight around your belly, or have a parent or sibling with type 2 diabetes. Perhaps you worry about needles, insulin, or losing your eyesight or kidney function. These are real fears, and they deserve a real conversation. Metformin is not a new, expensive celebrity drug—it is a cheap, well-studied, first-line medication that can change the direction of your health. This article explains why you should ask your doctor about it.

Interest: What is metformin and why do doctors trust it?

Metformin belongs to a class called biguanides. It has been used for more than 60 years and is the first-choice oral medicine for type 2 diabetes in Australia and worldwide. It works mainly by reducing how much glucose your liver releases into your blood and by making your muscles and tissues more sensitive to insulin. Unlike some diabetes drugs, metformin does not make your pancreas pump out extra insulin, so when used alone it rarely causes dangerous low blood glucose (hypoglycaemia).

What is the role of metformin in diabetes prevention programs?

In diabetes prevention programs, lifestyle changes—such as the Australian Life! program or similar state-based programs—remain the first step. But evidence from the large US Diabetes Prevention Program showed metformin reduced progression from prediabetes to type 2 diabetes by about 31% compared with placebo. Lifestyle change reduced it by about 58%, but many busy adults find sustained lifestyle change difficult. Therefore, Australian doctors may consider metformin for high-risk people with prediabetes, especially if you have a BMI above 35, are younger than 60, had gestational diabetes, or your HbA1c keeps rising despite diet and exercise. Metformin is not a replacement for healthy eating and movement, but it can be a practical, low-cost partner.

Desire: Why patients aged 30+ ask for metformin

Imagine seeing your next blood test show a lower HbA1c, feeling steadier energy through the afternoon, and knowing you are actively protecting your eyes, kidneys, and heart. People often tell me they feel more stable energy, fewer sugar crashes, and less worry about their future once their glucose is controlled. Metformin can modestly help with weight loss or at least prevent weight gain, unlike some diabetes medications. It has a strong long-term safety record. In the UKPDS study, metformin was associated with reduced diabetes-related complications and mortality in overweight people with type 2 diabetes. For many people, starting metformin early can delay or reduce the need for stronger medications or insulin. That matters if you are afraid of injections.

What is the PBS listing for metformin?

In Australia, metformin is subsidised by the Pharmaceutical Benefits Scheme (PBS) for type 2 diabetes when diet and exercise have not worked well enough. The PBS covers both immediate-release and extended-release forms. If you have a Medicare card, you pay a set co-payment. As of 2025, the general co-payment is $31.60 and the concession co-payment is $7.70. Many pharmacies, however, discount private scripts well below this. Metformin is not PBS-subsidised for prediabetes or polycystic ovary syndrome (PCOS), so those scripts are private—but they are still usually very affordable.

Cost of metformin at Chemist Warehouse vs Priceline?

Metformin is already one of the cheapest prescription medicines in Australia. Private script prices for the generic 500 mg immediate-release tablets (100 pack) are often lower than a cup of coffee. Chemist Warehouse typically has the lowest in-store price, while Priceline may be slightly higher but may price match. The table below is indicative only; always check your local pharmacy.

Ask for the generic “metformin hydrochloride” rather than a brand name. If you need extended-release metformin, it may cost slightly more, but it is still very affordable.

How often to test B12 on long-term metformin?

Long-term metformin can reduce vitamin B12 absorption in the gut. Low B12 can cause fatigue, memory fog, pins and needles, balance problems, and even nerve damage. The symptoms can be mistaken for normal ageing, so it is important to monitor. I recommend a baseline B12 before starting metformin, then regular checks as shown below.

Should I take a B12 supplement with metformin?

Not everyone needs a B12 supplement, but it is worth discussing with your GP. If your B12 is low or borderline, you should take a supplement. Many doctors recommend low-dose oral cyanocobalamin or methylcobalamin 1000 micrograms daily. It is cheap, safe, and water-soluble, meaning your body excretes excess. Routine supplementation is reasonable for long-term metformin users, especially if you have risk factors. Do not ignore low B12—it can cause irreversible nerve problems if left untreated.

Is metformin safe while breastfeeding?

Yes. Metformin passes into breastmilk in tiny amounts, and studies have not found harmful effects in breastfed babies. International lactation guidelines and Australian hospital guidance generally consider metformin compatible with breastfeeding. If you have type 2 diabetes or PCOS and are breastfeeding, metformin may be a safer option than many alternatives. Always discuss your individual situation with your GP, obstetrician, and paediatrician, but do not stop a prescribed medicine without medical advice.

Does metformin affect thyroid lab tests?

Metformin can lower the blood level of TSH (thyroid-stimulating hormone) in people being treated for an underactive thyroid, even when the free T4 and free T3 are normal. This is usually a laboratory effect, not a sign that your thyroid has suddenly changed. If you take levothyroxine, tell your doctor you are on metformin so they interpret your thyroid tests correctly. Do not change your thyroid medication based on a single TSH result.

Can metformin cause itching?

Itching is uncommon but possible with metformin. In most cases it is mild and settles, but it can occasionally be a sign of an allergic reaction or, rarely, liver irritation. If you develop itching with a rash, hives, swelling of the face or tongue, difficulty breathing, or dark urine, stop the metformin and seek urgent medical help. Isolated mild itching should still be reported to your GP, but it is not a reason to panic. Most side effects can be managed with dose changes or switching to extended-release.

Common side effects and practical solutions

Action: Your next step

Metformin is not a miracle, but it is one of the most valuable, affordable, and evidence-based tools we have for type 2 diabetes and high-risk glucose control. If you are over 30 and have been told your blood sugar is creeping up, have a family history, or want to protect your heart, eyes, kidneys, and nerves, book a GP appointment. Ask specifically: “Is metformin right for me?” Ask for an HbA1c test and a baseline B12. If prescribed, compare prices at Chemist Warehouse and Priceline, start low, take it with food, and set a reminder to recheck B12. A small white tablet today may save you from much bigger problems tomorrow.

Talk to your GP today about whether metformin is suitable for you.