GLP-1 medicines: the evidence, minus the hype
Made with AI tools and overseen by an Australian GP · Updated 8 November 2026
Semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro) and their relatives copy gut hormones that control blood sugar and appetite. They’re genuinely effective. They’re also not magic, not cheating, and not for everyone.
Quick answer: GLP-1 medicines are weekly injections (and some tablets) that copy gut hormones, lowering blood sugar and appetite. They’re used for type 2 diabetes and, for some brands, weight management. In the main trials, people lost about 15% (semaglutide) to 21% (tirzepatide) of their weight. Gut side effects are common, and weight usually returns after stopping.
What they are
- Semaglutide: Ozempic (type 2 diabetes) and Wegovy (weight management).
- Tirzepatide: Mounjaro. It copies two gut hormones, GIP and GLP-1.
- Older relatives: liraglutide and dulaglutide (Trulicity).
- Brand names are listed so you can recognise them, not as a recommendation.
How they work
- They boost insulin when blood sugar is high.
- They slow stomach emptying, so you feel full sooner and for longer.
- They act on the brain’s appetite centres, turning down hunger and “food noise”.
Who they’re for
- Type 2 diabetes, alongside diet and activity.
- Weight management in adults with obesity, or overweight with a weight-related condition (trials enrolled people with a BMI of 30 or more, or 27 or more with a related condition).
- Heart protection: in SELECT, semaglutide cut heart attacks, strokes and heart deaths by 20% (6.5% vs 8.0%) in people with heart disease and overweight but no diabetes.
- Sleep apnoea with obesity: tirzepatide is TGA-approved for this.
- Not for: pregnancy or breastfeeding, or people with a personal or family history of medullary thyroid cancer or MEN 2.
What results look like
- Semaglutide 2.4 mg (STEP 1): 14.9% average weight loss vs 2.4% on placebo over 68 weeks.
- Tirzepatide (SURMOUNT-1): 15.0–20.9% vs 3.1% over 72 weeks, depending on dose.
- Head to head (SURMOUNT-5): 20.2% on tirzepatide vs 13.7% on semaglutide. Full comparison: semaglutide vs tirzepatide.
- These are averages. Some people lose much more, some much less.
GLP-1 guides
- Side effectsSide effectsNausea, diarrhoea, constipation and hair loss, with the trial percentages next to placebo.
- CompareSemaglutide vs tirzepatideOzempic vs Mounjaro: weight loss head to head, diabetes, heart benefits and side effects.
- StoppingStoppingMost weight comes back within a year. What the withdrawal trials found, and how to plan.
- MuscleMuscle loss and proteinAbout a quarter of the weight lost is lean tissue. What protein and strength training can do.
- PregnancyPregnancy and contraceptionHow long to stop before trying, and why Mounjaro can make the pill less reliable.
- ProceduresSurgery and anaesthesiaKeep taking it, have a 24-hour clear fluid diet first, and tell your anaesthetist.
- SafetyCompounded and fake productsAustralia banned compounded copies in 2024. Fake pens, FDA harm reports and staying safe.
- AccessPBS and cost in AustraliaOzempic for type 2 diabetes only. Wegovy recommended but not listed. Mounjaro: no PBS.
- SafetyRare but serious risksGallbladder, pancreatitis, NAION and the thyroid warning, in real numbers.
- FAQCommon questionsAlcohol, hair loss, “Ozempic face”, how long to take it, and when it doesn’t work.
Not a miracle, not cheating. It’s a hormone medicine for a long-term condition. It turns down hunger; protein, sleep, movement and follow-up still do a lot of the work. Whether one suits you is a conversation with your doctor.
More on Malady Wise
- GLP-1 medicines compared: every brand, its uses and the full side-effect list.
- Semaglutide and tirzepatide medicine guides.
- Weight-loss medicines, including non-GLP-1 options.
- Fact sheets: weight and obesity, type 2 diabetes, prediabetes, fatty liver.
- Tool: BMI calculator.
Need a brain break? Play Dxtective, the daily diagnosis puzzle, or browse all medical games. Free, no sign-up.
Common questions
What is a GLP-1 medicine?
A medicine that copies GLP-1, a gut hormone released after eating. It boosts insulin when blood sugar is high, slows stomach emptying and reduces appetite. Semaglutide, tirzepatide, liraglutide and dulaglutide are examples.
Is Ozempic the same as Wegovy?
Both contain semaglutide. Ozempic is used for type 2 diabetes and Wegovy for weight management.
Which GLP-1 medicine causes the most weight loss?
On current evidence, tirzepatide. In the head-to-head SURMOUNT-5 trial, people lost 20.2% of their weight on tirzepatide versus 13.7% on semaglutide over 72 weeks.
Do I have to take a GLP-1 medicine forever?
The benefits last only while you take it. In trials, most people regained much of the weight within a year of stopping. How long to continue is a decision for you and your doctor.
Are GLP-1 medicines on the PBS?
Only for type 2 diabetes (Ozempic and Trulicity, when criteria are met) as of November 2026. None are subsidised for weight loss, and Mounjaro isn’t on the PBS for any use.
Evidence and more information
- Wilding et al, NEJM 2021: STEP 1, semaglutide 2.4 mg for weight management (weight loss, side-effect and gallbladder rates)
- Jastreboff et al, NEJM 2022: SURMOUNT-1, tirzepatide for obesity
- Aronne et al, NEJM 2025: SURMOUNT-5, tirzepatide versus semaglutide
- Lincoff et al, NEJM 2023: SELECT, semaglutide and heart outcomes in people without diabetes
- TGA: Updated contraception advice for Mounjaro (tirzepatide)
- US FDA prescribing information for Wegovy (semaglutide), February 2026: side-effect table, warnings
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