Various brands of metformin hydrochloride 1000 mg immediate-release tablets are in shortage. This is due to manufacturing issues in some cases, which has led to an unexpected increase in consumer demand for other brands.
Metformin hydrochloride is used in the treatment of type 2 diabetes mellitus.
Up-to-date information about the shortages of individual brands of metformin hydrochloride 1000 mg immediate-release is published on the Medicine Shortage Reports Database - external site, which can be searched by the medicine’s trade name (brand) or active ingredient (metformin).
To help manage the shortages, we have made a Serious Scarcity Substitution Instrument (SSSI) that starts on 28 May 2025. It allows a pharmacist to dispense an alternative brand, strength or formulation, if appropriate, without a new prescription. See below for information about the SSSI for patients, pharmacists and prescribers.
Information for patients
We understand the importance of a reliable supply of this medicine for patients with diabetes. We also appreciate the concern and frustration this shortage may cause.
As substitute medicines are available, we have approved substitutions your pharmacist can make without a new prescription. This may mean you will need to switch between different brands, strengths and formulations of metformin when the medicine prescribed for you is unavailable.
If substitution is not right for you, your pharmacist will refer you back to your doctor for review.
When you are offered a substitute medicine:
- it may contain a different strength or formulation of the same active ingredient (metformin) that your doctor prescribed
- the pharmacist will supply the correct total dose that your doctor prescribed
- let your pharmacist know if you are allergic or intolerant to certain ingredients, as the excipients (inactive ingredients) may vary between brands; you can also find information about excipients in the Consumer Medicine Information (CMI) leaflet available from your pharmacist or on the TGA website.
If your pharmacist offers you a substitute medicine, they should explain the differences and how to take the medicine you have been switched to. Follow instructions on how to take the substitute medicine carefully. This may be different from how you currently take your metformin medicine.
Talk to your doctor or pharmacist if you have any questions about this substitution.
If you are unable to fill your prescription or do not consent to the substitution, speak to your doctor about other options for your situation.
Information for prescribers
Consider the current shortage of metformin 1000 mg immediate-release tablets when prescribing for your patients, particularly when initiating new patients.
Your patients may need to switch between different brands, strengths and formulations of metformin when the prescribed medicine is unavailable.
The pharmacist may give your patient a different dosage form or strength of metformin to make up their daily dose. In some cases, the pharmacist may refer your patient to you for a review of their treatment.
When a pharmacist offers your patient a substitute medicine, they may give information and guidance on how to take the substitute product or they may recommend the patient contact you for this information. Consider checking how your patient is using the substitute medicine at their next appointment.
If a patient is unable to fill their prescription or does not consent to the substitution, the pharmacist will advise them to contact you to access suitable treatment.
Information for pharmacists
The SSSI allows you to dispense a substitute medicine in place of the prescribed 1000 mg immediate-release tablet, using this order of preference:
- the prescribed formulation and strength (metformin 1000 mg immediate-release tablet)
- an alternative strength of the same formulation (metformin 500 mg immediate-release tablets)
- a different strength and formulation of the prescribed medicine (metformin 500 mg or 1000 mg immediate-release or modified/extended-release tablet).
You can do this without prior approval from the prescriber if you follow the Specific permitted circumstances (in Schedule 1) and General permitted circumstances (in Schedule 2) of the SSSI.
You must provide the patients with enough substitute medicine to maintain the same duration of treatment (see Pharmaceutical Benefits Scheme considerations below).
Other notes for pharmacists
When providing a substitution, consider that patients may still have remaining metformin product at home. As substitution may require a change in formulation or dose, the new dosing instructions must be explained clearly to patients to ensure the substitute is taken safely.
You are encouraged to use your professional and clinical judgement to determine whether substitution is suitable for a patient and to gain their consent.
Clinical experts consider that due to the differences between immediate-release and modified-release formulations, prescriptions for more than 2 g of immediate-release metformin must not be substituted under the SSSI. These patients should be referred to their prescriber.
You should also refer patients to their prescriber in other situations when substitution is unsuitable, including if:
- an appropriate substitutable medicine is not available
- they are a child, and metformin immediate-release substitutes are not available
- they have difficulty swallowing, making an available substitute unsuitable
- they cannot take a modified/extended-release substitute due to gastrointestinal intolerance
- there are safety concerns, such as difficulties in following substitution instructions
- alternative treatments other than substitution may be more appropriate.
When you use the SSSI to substitute the scarce and substitutable medicines:
- you must instruct the patient on how to take the substitute tablet/s, or refer them to their prescriber, GP or nurse for guidance
- you can use Consumer Medicines Information (CMI) leaflets to help explain the substitution to patients and to get their consent; you may need to use translation services, a carer or organisations such as a local Aboriginal Community Controlled Health Organisation (ACCHO) if needed to ensure the patient fully understands the situation.
Inform the prescriber by email, fax or phone as soon as is practical after you make the substitution.
Pharmaceutical Benefits Scheme (PBS) considerations
When you give the patient enough of the substitute medicine to maintain the same duration of treatment as the prescribed medicine, this may exceed the PBS-listed maximum quantity.
In this case, you may use the authority prescription number ‘00000246’ and disregard the PBS Online warning (reason code 151). If the substitutable medicine is an authority-approved prescription, the PBS Online warnings (reason code 162 or 163) can be disregarded.
Example: Ms Braun is a healthcare card holder with a PBS prescription for metformin 1000 mg immediate-release tablets, quantity of 90, at a dose of one tablet twice daily. However, her pharmacist does not have any metformin 1000 mg immediate-release tablets in stock.
They do have metformin 500 mg immediate-release tablets in stock, so the pharmacist can dispense 180 of these tablets and, despite the increased quantity, Ms Braun will still pay the standard PBS co-payment of $7.70.
The pharmacist should advise Ms Braun to take two 500 mg tablets twice daily to match her prescribed dose and highlight any differences between the products.
You can find more information about PBS subsidy arrangements for medicines substituted using an SSSI on the PBS website.
General information
Please note that the dates given for this shortage may change and we encourage you to check the Medicine shortage reports database - external site for updates about the supply of metformin hydrochloride products.
Please also keep in mind that we can work with pharmaceutical companies to communicate information about medicine shortages to health professionals and patients, but we cannot compel companies to increase supply or apply to have their products subsidised on the PBS.
While we can suggest approaches to manage the supply of medicines during shortages, we do not have the power to regulate the clinical decisions of health professionals.
We will continue to monitor the supply of metformin hydrochloride immediate-release tablets and work with the suppliers and relevant health professionals to update this advice if needed.
Reporting problems
Consumers and health professionals are encouraged to report problems with medicines or vaccines. Your report will contribute to the TGA's monitoring of these products.
The TGA cannot give advice about an individual's medical condition. You are strongly encouraged to talk with a health professional if you are concerned about a possible adverse event associated with a medicine or vaccine.