GLP-1 Medicines in Australia: How They Work, and What the TGA Has Actually Approved

The short version

• GLP-1 medicines copy gut hormones your body already makes after a meal. They slow the stomach, blunt appetite and change how much food it takes before you feel done.
• In Australia, the TGA has registered Mounjaro (tirzepatide) and Wegovy (semaglutide 2.4 mg) for weight management. Both are prescription only.
• Ozempic is not one of them. Ozempic is semaglutide registered for type 2 diabetes.
• Zepbound does not exist here. That is the American brand for the same drug we call Mounjaro.
• Registered is not the same as subsidised. The PBS page covers that part.

What the medicines actually do

When you eat, your gut releases hormones that tell the rest of your body a meal has arrived. One of them is GLP-1. It nudges insulin up when blood glucose rises, slows how quickly the stomach empties, and sends a signal to the appetite centres in the brain that you have had enough. It is a normal part of eating that nobody notices until it is amplified.

These medicines are long-acting copies of that signal. Semaglutide works on the GLP-1 receptor. Tirzepatide works on GLP-1 and on a second receptor, GIP, which is another gut hormone in the same family. Because the copies last for days rather than minutes, the "I have eaten" signal is present most of the time instead of arriving after a meal and fading.

What people describe day to day is fairly consistent. Portions that used to feel normal feel like too much. The mental noise about food quietens down, and a lot of people find that the most striking part. Alcohol often loses some of its appeal. None of this is willpower arriving late. It is a hormone signal being turned up.

Two things follow. First, the effect depends on the medicine being in your system, which is why stopping usually brings appetite back. Second, eating less makes it very easy to eat badly: less food overall often means less protein, and protein is what protects muscle while you lose weight. That is a big part of why keeping a record matters more on these medications, not less.

What the TGA has registered

Registration means the TGAhas assessed a medicine for a particular use and entered it on the Australian Register of Therapeutic Goods. It is the answer to "may this be sold here, for what". It is not a comment on cost, and it is not a recommendation for any individual.

All three are prescription only, which in Australia also means they cannot be advertised to the public. That is why this page reads like a reference rather than a sales pitch, and why you will not find a "get started" button pointing at a supplier anywhere on it.

Ozempic is doing a different job

Ozempic and Wegovy contain the same active ingredient, semaglutide, at different doses and registered for different things. Ozempic is the diabetes brand. Wegovy is the weight management brand, and it goes to a higher maximum dose.

This mattered a great deal during the shortages. Demand for weight loss ran well ahead of supply, and the TGA asked prescribers to prioritise the people with type 2 diabetes who relied on Ozempic for their glucose control. If you have read old Australian news coverage about people being unable to fill scripts, that is the story behind it.

Prescribing Ozempic for weight loss is off-label. Off-label prescribing is legal and common across medicine, and it is a decision for a prescriber who knows your history, but it is worth knowing which side of the line you are on when you read the packet.

Brands you will read about that are not sold here

• Zepbound. The American brand name for tirzepatide used for weight management. Same molecule as Mounjaro, different label, not sold in Australia under that name. American dosing articles about Zepbound are describing our Mounjaro.
• Foundayo and the oral GLP-1s. The United States approved an oral once-daily GLP-1 tablet in 2026. Being approved by the FDA has no effect in Australia. Anything new has to go through the TGA separately before it can be sold here.
• Retatrutide. Still investigational everywhere. Anything sold online under that name is not an approved medicine.

This is worth holding on to generally: an FDA approval headline is news, not availability. Australian availability is a question for the TGA, and Australian cost is a separate PBS question after that.

What the trials found

Trial averages are useful for calibration and useless as a prediction about you. Two large randomised trials give the headline numbers most articles are quoting, usually without saying which trial or how long it ran.

• Semaglutide 2.4 mg (STEP 1). Average weight change of −14.9% at 68 weeks, against −2.4% on placebo (Wilding et al., NEJM 2021).
• Tirzepatide (SURMOUNT-1). Average weight change at 72 weeks of −15.0% on 5 mg, −19.5% on 10 mg and −20.9% on 15 mg, against −3.1% on placebo (Jastreboff et al., NEJM 2022).

Read those as ranges rather than promises. They are averages across thousands of people, and the spread underneath an average is wide: in SURMOUNT-1 some participants lost more than 20% of their body weight and others lost very little. Everyone in both trials also received diet and activity support, and everyone was taking the medicine under supervision at doses that had been stepped up over months. Your result depends on your dose, how long you stay on it, what else is going on in your life, and a fair amount of biology nobody can predict in advance.

Side effects, and the ones that matter

The common ones are digestive and they cluster around dose increases: nausea, constipation or diarrhoea, reflux, burping, and a kind of early fullness that can tip into feeling unwell if you push through it. For most people these ease over a few weeks at a steady dose. They are the reason doses are stepped up slowly rather than started high.

A few things are worth flagging rather than tolerating quietly.

• Severe, persistent stomach pain, especially pain that bores through to your back and comes with vomiting. Get assessed.
• Vomiting you cannot keep fluids down through. Dehydration is the most common reason people on these medicines end up in hospital, and it is preventable.
• Changes in mood or thoughts of self-harm. The product information across this class has been aligned by the TGA to cover the potential risk of suicidal thoughts or behaviours. If your mood shifts, tell someone.
• Losing weight fast while eating very little. Not a side effect exactly, but it is how people lose muscle rather than fat, and it is the thing worth catching early.

The full and current list of side effects is in the Consumer Medicine Information leaflet for whichever medicine you are prescribed, which your pharmacist will give you and which the TGA also publishes. That leaflet, not an article, is the authoritative list.

Compounded GLP-1s are no longer allowed

This one is specifically Australian and it caught a lot of people out. From 1 October 2024, changes to the Therapeutic Goods Regulations removed GLP-1 receptor agonists from the exemption that lets pharmacists compound medicines for individual patients. Compounded semaglutide and its relatives can no longer be made up and supplied here.

The practical version: if something is being offered as a cheaper compounded or "research grade" GLP-1, it sits outside the system that checks what is actually in the vial. There is no registered product behind it, no batch testing you can rely on and no recourse. If you were using a compounded product before the change, that is a conversation to have with your GP rather than something to solve online.

What tracking is actually for

Appointments are short and memory is unreliable. Three months in, almost nobody can say with any confidence which week the nausea started, what their weight was doing before the last dose step, or whether protein has quietly collapsed since portions got smaller. A record answers all three in about ten seconds.

That is the whole idea behind Healthcount. Weight, food, doses and symptoms in one place, in kilojoules, with a trend line that ignores the daily wobble. It does not tell you what to do. It gives you and your GP something better than recollection to look at.

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