GLP-1 medications in Australia
A science-backed explainer.
Clinician reviewed · Last updated June 2026
A new class of injectable medication has reshaped how obesity is treated in Australia. The conversation around it has moved fast, often faster than the evidence. This is a plain English explainer of what GLP-1 medications are, how they work, what the trials actually show, and the questions a thoughtful clinician will ask before considering them as part of a longer program. No hype, no shortcuts, no advertising of specific products. Just the science as it stands in 2026.
GLP-1 medications are a class of prescription-only therapies that mimic a gut hormone the body produces naturally after eating. They reduce appetite, slow stomach emptying, and improve blood glucose regulation. In Australia they are Schedule 4 medicines, available only with a prescription after a clinical assessment, and are used for type 2 diabetes and, in some cases, chronic weight management.
What GLP-1 medications actually are
GLP-1 stands for glucagon-like peptide-1, a hormone released by the gut in response to food. It signals the pancreas to release insulin, suppresses glucagon, slows gastric emptying, and acts on appetite centres in the brain. The body produces it in small amounts and breaks it down quickly.
GLP-1 receptor agonists are synthetic molecules designed to mimic that hormone, but with a longer half-life. Some are weekly injections, some daily. The most widely discussed agents internationally include semaglutide (sold as Ozempic for type 2 diabetes and Wegovy for chronic weight management) and tirzepatide (sold as Mounjaro in Australia, and Zepbound in some other markets). Tirzepatide is technically a dual agonist, acting on both GLP-1 and a second gut hormone called GIP (glucose-dependent insulinotropic polypeptide).
In Australia, these medicines sit on the Australian Register of Therapeutic Goods (ARTG) for specific approved indications. Under the Therapeutic Goods Act 1989, prescription medicines cannot be advertised to consumers, which is why responsible clinical content discusses the category and the mechanism, not specific brands as products to obtain.
How they work
The mechanism is broader than most people assume. GLP-1 receptor agonists work in at least four ways simultaneously:
Dual GIP and GLP-1 agonists add a second pathway that appears to modulate fat metabolism and energy expenditure, which contributes to the larger weight reductions seen in head-to-head studies.
What the evidence shows on weight outcomes
The STEP trials (semaglutide) and SURMOUNT trials (tirzepatide) have produced the most reliable evidence to date.
STEP 1, the pivotal trial of semaglutide 2.4 mg in adults with obesity without type 2 diabetes, showed mean weight loss of around 14.9 percent at 68 weeks. SURMOUNT-1, the equivalent trial for tirzepatide, reported 15 to 21 percent weight loss at 72 weeks depending on dose. The first head-to-head comparison, SURMOUNT-5, published in NEJM in 2025, found tirzepatide produced a mean weight reduction of 20.2 percent compared with 13.7 percent for semaglutide at 72 weeks.
Real-world data tends to be more modest. A 2025 analysis of US clinical practice showed average one-year weight loss of around 14 percent on semaglutide 2.4 mg and 16.5 percent on tirzepatide, lower than trial settings, in part because patients in the real world often do not reach the maximum doses used in trials.
Two honest caveats. The trial populations had structured support, including dietetic input and adherence monitoring, which the average person on a script does not receive. And response varies. Roughly one in seven patients in pivotal trials lost less than five percent of body weight. This is a medication, not a guarantee.
The lean muscle question
This is where the 2026 conversation has shifted, and it matters.
When anyone loses weight quickly, some of what they lose is lean tissue. Earlier reports suggested that 25 to 40 percent of weight lost on GLP-1 medications was lean mass, which alarmed clinicians who understand what muscle does for metabolic health, glucose handling, and longevity.
More recent analysis has refined that picture. A 2025 systematic review in the International Journal of Obesity confirmed that lean mass loss occurs but is proportionally smaller than fat loss. Work by the UC Davis group has shown that much of what was originally counted as "lean" loss came from liver and organ tissue rather than skeletal muscle, and that the skeletal muscle loss itself is closer to what happens with any caloric restriction, around 20 percent of total weight lost.
The clinical response is now clearer than it was a year ago. Resistance training and adequate protein intake meaningfully attenuate muscle loss during treatment. The current expert consensus supports protein intake in the range of 1.2 to 2.0 grams per kilogram of body weight, structured resistance training at least twice weekly, and serial body composition tracking rather than scale-only monitoring.
This is why a program that prescribes a medication without addressing what is being lost alongside the fat is doing half the work. Body composition, not weight, is the measure that matters. See our body composition primer for how this is assessed.
Side effects and safety
Most side effects are gastrointestinal. Nausea, reflux, constipation, and occasional vomiting are common, particularly during dose escalation. These usually settle as the body adjusts, and slower titration generally helps.
Less common but clinically important issues include pancreatitis, gallbladder disease, and dehydration risk during illness. There is an ongoing watching brief on thyroid C-cell tumours based on rodent data, which is why a personal or family history of medullary thyroid carcinoma is a contraindication.
In December 2025, the TGA aligned class warnings across all GLP-1 receptor agonists in Australia to include guidance on monitoring for new or worsening depression and suicidal thoughts. Current evidence has not shown a higher overall rate of depression compared to placebo, but the signal is being tracked and patients are advised to report any mood changes promptly to their prescriber.
Long-term safety data is reassuring but still accumulating. These medicines have been in widespread use for diabetes for over a decade, and for weight management for several years. Cardiovascular outcome trials have shown reductions in major adverse cardiovascular events in specific populations. As with any therapy intended for long-term use, the right answer is structured monitoring, not assumption.
A note on grey-market and compounded products. From 1 October 2024, the TGA prohibited pharmacists from compounding medicines containing GLP-1 receptor agonist analogues. The TGA has also issued repeated safety advisories about unregistered "GLP-1 peptide" products sold online, often as oral drops, which are unapproved, unverified, and in some cases counterfeit. Anything sold outside the regulated prescription pathway should be treated with serious caution.
What happens when you stop
This is one of the most-searched questions and the answer is important.
In the STEP 1 trial extension, participants who stopped semaglutide regained approximately two-thirds of the weight they had lost within one year. The SURMOUNT-4 trial of tirzepatide showed a similar pattern, with more than 50 percent of lost weight regained over 52 weeks after discontinuation. A 2026 meta-analysis in The Lancet eClinicalMedicine modelled regain plateauing at around 60 weeks post-cessation.
Real-world data is slightly more nuanced. Some patients, particularly those who built durable changes in eating patterns, body composition, and physical activity during treatment, regain less. The clinical implication is unambiguous: obesity is a chronic condition, and these medications are best thought of as long-term tools, not a temporary intervention with a clean exit.
If discontinuation is the goal, it should be planned, supported, and gradual, with the lifestyle scaffolding already in place.
Who they suit, and who they do not
GLP-1 medications can be appropriate, after a full clinical assessment, for adults with type 2 diabetes, or for adults meeting defined BMI and comorbidity criteria where lifestyle measures have not produced sufficient response.
They are not appropriate for everyone. People with a history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2, a history of pancreatitis, severe gastrointestinal disease, certain eating disorders, or who are pregnant or trying to conceive, are generally not candidates. Anyone seeking rapid cosmetic weight loss without a clinical indication is also outside the appropriate population.
The honest summary: these are powerful prescription medicines with a real risk profile, and they belong inside a clinical relationship that includes baseline screening, structured follow-up, and an exit plan.
Book a consult to discuss whether a medically supervised weight loss program is the right fit for your situation.
How a clinician-led program differs from a script-mill
The Australian market has filled with online services that prioritise speed of script over depth of care. The clinical case against that model is straightforward.
A clinician-led program starts with a full medical history, baseline pathology, body composition assessment, and a discussion of goals that includes the possibility that medication is not the right answer. If medication is clinically appropriate, it is one component of a broader plan that includes nutrition, resistance training, sleep, and structured monitoring. Side effects are managed actively. Body composition is tracked, not just weight. And the off-ramp is part of the plan from day one, not an afterthought.
This is the model our weight loss program is built around, and it is the model the evidence supports.
Frequently asked questions
They mimic a natural gut hormone that reduces appetite, slows stomach emptying, and improves blood glucose regulation. The net effect is reduced energy intake without conscious restriction.
The class has over a decade of use in diabetes and several years in weight management, with reassuring but still accumulating long-term data. They are considered chronic therapies and require structured medical monitoring, including periodic review of mood, gastrointestinal symptoms, and metabolic markers.
Trial data shows most people regain a significant portion of lost weight within a year of stopping, around two-thirds in the STEP 1 extension. This reflects the chronic nature of obesity. Discontinuation should be planned and supported, not abrupt.
Some lean tissue loss occurs with any rapid weight loss. Recent evidence suggests skeletal muscle loss on GLP-1 therapy is similar to that seen with caloric restriction alone, around 20 percent of total weight lost. Resistance training and protein intake of 1.2 to 2.0 grams per kilogram of body weight meaningfully reduces it.
They are Schedule 4 prescription medicines. Eligibility is determined by an AHPRA-registered prescriber based on clinical indication, BMI, comorbidities, and medical history. They are not appropriate for everyone.
As of June 2026, semaglutide (Ozempic) is PBS-listed for type 2 diabetes under specific criteria. GLP-1 medicines used for chronic weight management, including Wegovy and Mounjaro for the weight indication, are not currently PBS-listed and are private prescription only. PBS status is reviewed regularly by the PBAC.
No. Since 1 October 2024, the TGA has prohibited the compounding of medicines containing GLP-1 receptor agonist analogues by pharmacists.
Baseline pathology and body composition assessment, an AHPRA-registered prescriber, active side effect management, structured nutrition and resistance training support, regular monitoring, and a clear discontinuation plan.
Ready to talk about a medically supervised program? Book a consult for a clinical assessment, or create a free account to explore the program at your own pace.