Summary and key information
Metformin is an oral antidiabetic medicine in the biguanide class commonly used to treat type 2 diabetes. It is usually given together with diet and exercise recommendations. Clinicians may prescribe metformin on its own or in combination with other glucose lowering therapies.
Common immediate release tablet strengths supplied in Australia include 500 mg and 850 mg. Extended release formulations are available with some brands, sometimes identified as XR or modified release.
For safety guidance and a summary of possible unwanted effects, see the sections on heads up notices and ill effects below.
Typical uses and beacons
Metformin is principally indicated for the management of hyperglycemia in adults and children with type 2 diabetes mellitus. It helps lower blood glucose and is often recommended as first-line pharmacotherapy when lifestyle measures alone are insufficient.
It is also used in combination regimens with other agents such as:
- Sulfonylureas
- DPP-4 inhibitors
- SGLT2 inhibitors
- GLP-1 receptor agonists
- Insulin when required for glycemic control
How metformin should be taken
Follow the prescription instructions from your doctor or nurse. If anything is unclear, ask your pharmacist for clarification.
- Take tablets by mouth, usually with a meal to reduce stomach upset.
- Keep dosing times consistent each day to maintain steady blood levels.
- Do not stop taking metformin abruptly without medical advice, even if you feel well.
- If you have difficulty swallowing tablets, ask your healthcare team about a substitute choice formulations.
Strengths offered and dosing information
Typical tablet strengths encountered in Australia include 500 mg and 850 mg for immediate-release preparations. Extended-release options are commonly offered in strengths compatible with once-daily dosing.
Prescribers usually start at a low dose and increase gradually to reduce gastrointestinal collateral effects. Dose adjustments are based on blood glucose response, tolerability, age, and kidney function. Only change your dose with medical informed direction.
An explanation of how the workflow comes together
Metformin reduces fasting and postprandial blood glucose through several the method by which it operatess including:
- Lowering hepatic glucose production.
- Decreasing glucose absorption from the gut.
- Enhancing insulin sensitivity in peripheral tissues.
Steps to take when a dose is missed
If a dose is missed, take it as soon as you remember unless it is nearly time for your next scheduled dose. Do not double the dose to compensate for a tablet you missed. Resume your prescribed schedule and contact your prescriber if you miss multiple doses.
Stowage and handling
- Store in a climate of about 20-25 C. Minor excursions to 15-30 C are usually permissible.
- Keep the product away from heat, damp conditions and direct sunlight. Please avoid storing in bathrooms.
- Ensure medicines are kept out of reach of youngsters and animals.
- Return unwanted or expired tablets to a pharmacy for safe disposal via the RUM program.
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Warning signals and recommended precautions
Do not take metformin if any of the following apply, unless your clinician advises otherwise:
- Known allergy to metformin or to any inactive ingredient within the product.
- Severe impairment of kidney function or significant liver disease.
- Conditions with reduced tissue oxygenation, for example severe heart failure, recent heart attack, or sepsis.
- Diabetic ketoacidosis.
- Severe dehydration or acute serious illness.
Additional safety pointers and watchful oversight:
- Assess kidney function before starting and periodically thereafter. Dose changes may be required for reduced renal function.
- Avoid heavy alcohol use because this can increase the risk of lactic acidosis and worsen negative effects.
- Inform your surgical or dental team that you take metformin. Temporary interruption may be advised around some procedures or when contrast media is used.
- Older adults may be more vulnerable to adverse reactions and to reduced kidney function; monitor carefully.
- Carry identification indicating you have diabetes and the medicine you take.
- Metformin on its own rarely causes low blood sugar, but the risk rises with missed meals, strenuous exercise, alcohol, or combination therapy with insulin or sulfonylureas.
- If you develop persistent vomiting, severe diarrhea, dehydration, or unexplained muscle pain and malaise, seek urgent medical attention as these can be signs of lactic acidosis.
Possible adverse consequences
Typical adverse events, which often settle after the first few weeks, include:
- Nausea, diarrhea or other stomach upset.
- Flatulence and indigestion.
- Headache symptoms or transient taste disturbance.
Seek immediate medical help for serious or life threatening symptoms such as:
- Severe allergic reactions with swelling of the face or throat, severe rash, or difficulty breathing.
- Chest pain or severe dizziness.
- Severe muscle weakness, unusual drowsiness, persistent vomiting or abdominal pain which may suggest lactic acidosis.
Therapeutic other options and comparison of prices (AUD)
Choice of therapy depends on blood glucose targets, kidney and liver function, cardiovascular history, weight considerations, tolerability, and cost. Commonly accepted substitutes or adjuncts include:
- Sulfonylureas (for example gliclazide) - inexpensive generics and often low out-of-pocket cost under PBS.
- DPP-4 inhibitors (for example sitagliptin) - moderate cost, many are PBS-listed for eligible patients.
- SGLT2 inhibitors (for example empagliflozin, dapagliflozin) - higher list price but PBS subsidy applies for many markers that point to.
- GLP-1 receptor agonists (for example semaglutide, dulaglutide) - usually higher private cost; PBS listing with criteria may reduce patient cost.
- Insulin preparations - variable cost and pricing model; many types are PBS-subsidised for eligible patients.
Rough a tariff framework guide in Australian dollars (indicative only):
- Generic metformin (private purchase): about AUD 5 to 30 per month depending on formulation and pack size; PBS co-payment usually limits patient cost for eligible prescriptions.
- Sulfonylureas: typically within PBS co-payment limits for prescription items, private cost often low.
- DPP-4 inhibitors: private cost may be higher but often PBS-listed; out-of-pocket commonly up to the PBS co-payment for eligible patients.
- SGLT2 inhibitors: private cost higher without subsidy; with PBS listing and eligibility patient cost often up to PBS co-payment.
- GLP-1 receptor agonists: private cost commonly over AUD 100 per month; with PBS criteria met patient cost may be substantially reduced.
Prices vary by brand, pharmacy and whether you receive the drug under the PBS. Ask your pharmacist about generic brands and your likely out-of-pocket expense.
Access and PBS with legal points in the Australian continent.
- Regulatory status: Metformin is a Schedule 4 prescription only medicine in the land of Australia. A valid prescription from an authorised prescriber is required.
- Pharmaceutical Benefits Scheme: Many metformin products are PBS-listed. Eligible patients pay the PBS co-payment per script, which is usually much lower than private prices.
- Substitution: Pharmacists may substitute brands with an equivalent generic product unless the prescriber has specified no substitution.
- Telehealth: Electronic and telehealth consultations may be used to obtain lawful prescriptions where permitted by current rules.
- Importing medicines: The TGA Personal Import Plan Outline permits limited personal importation in certain circumstances. Check current TGA guidance before ordering overseas supplies.
- Disposal and returns: Return unused or expired medicines to a pharmacy; do not dispose of tablets in household rubbish or down the drain.
- Advertising: Direct-to-consumer advertising of prescription medicines is restricted and regulated by Australian law and industry codes.
Online resources for further study with contact details
If you have questions specific to your situation, speak with your prescribing doctor, diabetes educator or pharmacist. Do not share prescription medicine with others.
For authoritative, up to date guidance consult the Therapeutic Goods Administration (TGA), the Pharmaceutical Benefits Scheme (PBS) website, or The medical term diabetes Australia for patient resources.
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