Attention: The silent burden of type 2 diabetes

Over 1.3 million Australians live with type 2 diabetes, and many more have prediabetes without knowing it. If you are over 30, you may already recognise the warning signs: fasting blood glucose creeping up, an HbA1c of 6.5–7.0%, tiredness after meals, weight settling around the middle, and a family history that worries you. You may also fear what comes next — insulin injections, kidney damage, heart attack, vision loss, or nerve pain.

The good news is that one of the oldest, most studied, cheapest and safest diabetes medicines is available in Australia, covered by the PBS, and recommended as first-line treatment by Australian and international guidelines. That medicine is metformin. This review answers the questions I hear in my clinic every day — so you can make a confident decision with your doctor.

Interest: Why metformin remains the first-line choice for Australian doctors

Metformin is a biguanide. It works mainly by reducing the amount of glucose your liver makes and improving your body’s sensitivity to insulin. It does not stimulate the pancreas, so it has a very low risk of hypoglycaemia when used alone. It is weight-neutral or can help modest weight loss, unlike some diabetes drugs that cause weight gain. It also has long-term cardiovascular benefits, which matters because diabetes increases heart attack and stroke risk.

As a doctor, I like metformin because it is predictable, effective, and has been used for more than 60 years. In Australia, it is TGA-approved and PBS-listed, meaning you pay a standard PBS co-payment rather than a private prescription price.

Desire: Your most common questions answered

1. Metformin and ACE inhibitors interaction — is it safe to take both?

Yes. If you take an ACE inhibitor such as perindopril or ramipril for high blood pressure or kidney protection, you can usually take metformin safely. There is no direct drug interaction between metformin and ACE inhibitors. In fact, the combination is very common because many people with type 2 diabetes also need blood pressure control and kidney protection.

The main precaution is that both metformin and ACE inhibitors can affect kidney function. You should have your kidney function (eGFR) checked before starting metformin and at least once a year. If your eGFR falls below 30 mL/min/1.73 m², metformin should be stopped. If your eGFR is 30–45, the dose should be reduced and monitored.

2. What is the TGA pregnancy category of metformin?

Metformin is listed as TGA Pregnancy Category C in Australia. This sounds alarming, but it does not mean metformin causes malformations. Category C means that there is limited human pregnancy data, and the medicine may have pharmacological effects that require caution. In practice, insulin is usually preferred for diabetes during pregnancy, but metformin is used under specialist supervision for some women with polycystic ovary syndrome (PCOS), gestational diabetes, or type 2 diabetes when the benefits outweigh the risks.

If you are planning pregnancy or become pregnant, do not stop metformin suddenly. Talk to your GP, endocrinologist, or obstetrician first. They will help you make the safest plan for you and your baby.

3. Can you take metformin with other supplements?

Generally, yes — but you need to know a few important points. Long-term metformin can reduce vitamin B12 absorption, so I check B12 levels annually in my patients. Low B12 can cause fatigue, pins and needles, memory fog, and anaemia. If your B12 is low, a supplement is safe and recommended.

Most standard supplements are fine with metformin, including a multivitamin, vitamin D, fish oil, and CoQ10. However, fibre supplements like psyllium can delay metformin absorption if taken at the same time — separate them by about two hours.

Be cautious with herbal products that claim to lower blood sugar, such as berberine, chromium, bitter melon, and high-dose cinnamon extract. They can add to metformin’s glucose-lowering effect and increase the risk of hypoglycaemia, especially if you are also taking other diabetes medicines. Always tell your doctor or pharmacist about all supplements.

4. What is the target HbA1c on metformin?

In Australia, the general target HbA1c for most adults with type 2 diabetes is ≤7.0% (53 mmol/mol). However, targets are individualised. For a younger, healthier person, a target of 6.5% (48 mmol/mol) may be appropriate. For an older or frail person, a target of 7.5–8.0% (58–64 mmol/mol) is often safer to avoid overtreatment.

Metformin alone typically lowers HbA1c by about 1.0–1.5% (11–16 mmol/mol). If your starting HbA1c is 8.5%, metformin alone may bring you close to 7.0%. If not, your doctor can add another medicine.

5. What is the role of metformin in managing hyperglycaemia in hospital?

In hospital, acute hyperglycaemia is usually managed with insulin because it works quickly and can be adjusted hour by hour. Metformin is not a rescue drug for very high glucose, diabetic ketoacidosis, or hyperosmolar hyperglycaemic state.

However, if you are admitted to hospital for a non-critical illness and are stable, eating, and have normal kidney and liver function, your usual metformin may be continued. It is often withheld on sick days — for example, if you are vomiting, dehydrated, septic, or about to have IV contrast or surgery — to reduce the rare risk of lactic acidosis. Before discharge, we recheck kidney function and restart metformin if safe.

6. Bioequivalence of generic metformin in Australia — can I trust cheaper brands?

Yes. In Australia, every generic metformin product must meet strict TGA bioequivalence standards. This means the generic version must deliver the same amount of active ingredient into your bloodstream over time as the original brand. The agreed international range is that the 90% confidence interval for AUC and Cmax falls within 80–125% of the originator.

Generic does not mean weaker. APO-Metformin, Sandoz Metformin, Alphapharm Metformin and others are therapeutically equivalent to Glucophage. If you switch brands, your blood glucose control should remain the same. Some people tolerate one brand better due to different inactive fillers; if you are stable on one brand, staying on it is reasonable.

7. Metformin and hepatitis B/C considerations

Metformin is not broken down by the liver, so it is generally safe in people with chronic hepatitis B or C who have stable liver function and no cirrhosis. However, if you have decompensated cirrhosis or active liver failure, metformin should usually be avoided because the liver plays a role in clearing lactate, and lactic acidosis risk may increase.

If you have hepatitis B or C, your doctor will monitor liver function tests, kidney function, and your viral load as usual. Some research suggests metformin may reduce liver fat accumulation and even lower the risk of liver cancer, but this is not currently the main reason we prescribe it.

8. What to look for when buying metformin online

Metformin is a prescription medicine in Australia. You should only buy it from a registered Australian pharmacy with a valid prescription from an Australian-registered doctor. This applies whether you buy in person or online.

Look for the AUST R number on the packaging — this means it is a registered prescription medicine. Avoid products with only an AUST L number, which are listed supplements, not actual metformin. Beware of overseas websites that sell metformin without a prescription; these products may be counterfeit, contaminated, or the wrong dose.

Action: Take control of your blood glucose today

Metformin is not a cure for type 2 diabetes, but it is one of the safest, cheapest, and most effective tools we have. It lowers HbA1c without causing weight gain or frequent hypos, and it protects your heart and blood vessels over the long term. For many Australians over 30, that means fewer worries about complications and a better quality of life.

Your next steps are simple:

1. Book a diabetes review with your GP. Ask for HbA1c, kidney function (eGFR), and vitamin B12 tests.
2. Discuss whether metformin is right for you. Bring up any liver, kidney, pregnancy, or supplement concerns you have.
3. If prescribed, start low and take it with food. This reduces stomach upset. If immediate-release upsets your gut, ask about extended-release metformin.
4. Fill your script at a registered Australian pharmacy — in person or online — and never buy from unregulated overseas sites.
5. Follow up in 3 months. We recheck HbA1c, adjust the dose if needed, and make sure you feel well.

If you have been delaying treatment because you fear injections, weight gain, or low blood sugar, metformin may be the gentle but powerful first step you need. Talk to your doctor today.

Doctor’s bottom line: Metformin is first-line for very good reasons — it works, it is safe for most people, it is cheap on the PBS, and it does not cause the weight gain or severe hypos that make diabetes management so frightening. If you are over 30 and living with high blood glucose, ask your GP whether metformin belongs in your treatment plan.