GLP-1 Weight-Loss Medicines: Benefits, Side Effects and Long-Term Use

A practical guide to semaglutide, tirzepatide and other incretin medicines — what they do, what benefits go beyond the scales, what side effects matter and what happens if treatment stops

GLP-1 medicines have changed obesity treatment.

For many people, they can reduce hunger enough to make sustained weight loss achievable after years of struggling with:

• appetite;
• cravings;
• repeated dieting;
• weight regain;
• obesity-related health problems.

In Australia, Wegovy (semaglutide) and Saxenda (liraglutide) are approved for chronic weight management. Mounjaro (tirzepatide) acts on both GIP and GLP-1 pathways and is approved for type 2 diabetes and chronic weight management.

These medicines are not simply stronger appetite suppressants.

They affect biological systems involved in:

• hunger;
• fullness;
• digestion;
• blood glucose;
• metabolic health.

And in selected patients, the benefits can extend well beyond the number on the scales.

The important question is:

“Is this medicine improving my health in a way that is effective, tolerable and sustainable?”

What does GLP-1 actually mean?

GLP-1 stands for glucagon-like peptide-1.

It is a hormone involved in:

• appetite;
• fullness after eating;
• insulin release;
• blood-glucose regulation;
• stomach emptying.

GLP-1 receptor agonist medicines mimic some of these effects.

Tirzepatide works somewhat differently because it activates both the GIP and GLP-1 receptors.

For many patients, the most obvious change is appetite.

People often describe:

• feeling full earlier;
• smaller portions being enough;
• less interest in snacking;
• fewer cravings;
• thinking about food less often.

That reduction in what is sometimes called “food noise” can make sustained weight loss much easier.

Which medicines are we talking about?

Semaglutide
Wegovy is semaglutide approved for chronic weight management.

Ozempic also contains semaglutide, but its Australian indication is type 2 diabetes.

Tirzepatide
Mounjaro is a dual GIP/GLP-1 medicine approved in Australia for both type 2 diabetes and chronic weight management.

Liraglutide
Saxenda is an older GLP-1 medicine used for chronic weight management.

The newer weekly medicines generally produce greater average weight loss than earlier obesity medicines, but the best treatment is not automatically the newest or strongest one.

How much weight can people lose?

There is wide variation.

In major obesity trials, semaglutide 2.4 mg produced average weight loss of around 15%.

Tirzepatide trials have produced average losses approaching 20% or more at higher doses in selected trial populations.

Those figures are impressive.

But they are averages, not guarantees.

One person may lose 8%.

Another may lose 15%.

Another may lose 25%.

Someone else may have very little response or stop because of side effects.

Treatment should not be judged by whether you match somebody else’s result on social media.

Is tirzepatide better than semaglutide?

In a direct 72-week head-to-head trial in adults with obesity without diabetes, tirzepatide produced greater average weight loss than semaglutide.

That is useful information.

But it does not mean tirzepatide is automatically the better medicine for every patient.

The decision can still depend on:

• side effects;
• diabetes;
• cardiovascular disease;
• sleep apnoea;
• pregnancy plans;
• cost;
• availability;
• individual response.

A medicine that produces slightly less weight loss but is affordable, well tolerated and sustainable may be the better treatment for a particular person.

What benefits can occur beyond weight loss?

This is one of the most important developments in the field.

Selected incretin medicines have demonstrated benefits in obesity-related conditions including:

• type 2 diabetes;
• cardiovascular outcomes in specific high-risk populations;
• obstructive sleep apnoea;
• obesity-related heart failure;
• metabolic fatty liver disease.

That means the value of treatment can sometimes be much larger than:

“I lost 15 kilograms.”

A patient may also see improvement in:

• blood glucose;
• blood pressure;
• mobility;
• sleep;
• liver health;
• cardiovascular risk.

The exact benefits depend on the specific medicine and the specific medical condition.

Not every GLP-1 medicine has proven benefit for every obesity-related disease.

What about sleep apnoea?

Tirzepatide is approved in Australia for obstructive sleep apnoea in adults with obesity.

That does not mean everyone with sleep apnoea should replace CPAP with an injection.

Sleep-apnoea treatment should still be individualised.

But it shows how obesity treatment is increasingly becoming part of treating the health consequences of excess weight, not simply treating appearance.

What about fatty liver?

Clinical studies suggest incretin medicines can improve metabolic fatty liver disease in selected patients, largely alongside weight loss and improvements in metabolic health.

But they should not be assumed to replace proper assessment of significant liver disease.

If fatty liver is present, management may still need to consider:

• fibrosis stage;
• diabetes;
• alcohol;
• cholesterol;
• cardiovascular risk;
• other causes of liver disease.

Weight-loss medication can be one part of the plan.

What are the common side effects?

The common problems are mainly gastrointestinal.

They include:

• nausea;
• vomiting;
• diarrhoea;
• constipation;
• bloating;
• reflux;
• abdominal discomfort.

These effects are often most noticeable:

• when the medicine is first started;
• after the dose increases;
• after very large meals;
• after rich or fatty food.

This is one reason doses are increased gradually.

Do I need to reach the maximum dose?

No.

The goal is not:

“Get to the highest dose as quickly as possible.”

The dose should balance:

• appetite control;
• weight response;
• health benefit;
• nutritional intake;
• side effects;
• cost.

Some people achieve excellent results at lower doses.

Others need further escalation.

A dose that leaves someone constantly nauseated and barely eating is not automatically a successful dose simply because weight is falling.

Nausea: how much is acceptable?

Some mild nausea during dose escalation can occur.

But there is an important difference between:

“I feel slightly queasy for a day or two.”

and:

“I am vomiting repeatedly and cannot keep fluids down.”

Seek medical review for:

• persistent vomiting;
• dehydration;
• severe or persistent abdominal pain;
• inability to eat or drink adequately;
• severe constipation.

Do not normalise major symptoms simply because the medicine is known to affect the gut.

What about gallstones and pancreatitis?

Rapid or substantial weight loss can increase gallstone risk, and gallbladder problems are recognised with these medicines.

Pancreatitis is uncommon but clinically important.

Severe, persistent abdominal pain, particularly when associated with vomiting, deserves medical assessment.

Do not assume that every episode of severe abdominal pain is simply part of the expected gastrointestinal side effects.

What happens to muscle while I lose weight?

Any significant weight loss can include some loss of lean tissue as well as fat.

That is why muscle preservation matters.

Useful strategies include:

• adequate protein;
• resistance exercise;
• regular physical activity;
• avoiding unnecessarily severe calorie restriction.

Particularly in older adults, the goal should not be:

lighter but weaker.

It should be:

lighter, stronger and metabolically healthier.

What if I barely feel hungry?

Reduced appetite is part of how these medicines work.

But having almost no appetite is not necessarily ideal.

It is still important to consume enough:

• protein;
• fluid;
• fibre;
• vitamins and minerals;
• overall nutrition.

If someone is living mainly on coffee and a few mouthfuls of food because they cannot face eating, the dose and treatment plan should be reviewed.

Successful weight treatment should improve health, not create malnutrition.

What is the new eye warning?

This is a new development in 2026.

On 23 July 2026, the TGA updated warnings across the GLP-1 receptor agonist class regarding non-arteritic anterior ischaemic optic neuropathy — NAION.

NAION is rare, but it can cause serious and potentially permanent visual loss.

If you develop sudden partial or complete loss of vision, seek urgent medical assessment.

The overall risk is low, but sudden visual loss should never be ignored.

What about depression or suicidal thoughts?

In late 2025, the TGA aligned warnings across the GLP-1 class regarding possible suicidal thoughts or behaviours.

Importantly, the available evidence was not sufficient to prove that these medicines cause suicidality.

Tell your healthcare professional if you develop:

• new or worsening depression;
• suicidal thoughts;
• significant behavioural change.

The purpose of the warning is appropriate monitoring, not assuming that these medicines commonly cause suicidal behaviour.

Why does my anaesthetist need to know?

These medicines can delay stomach emptying.

That means some people may still have stomach contents present despite usual fasting before anaesthesia or deep sedation.

This can increase the risk of regurgitation and aspiration.

Therefore:

Tell the anaesthetist or procedural team that you are taking a GLP-1 or GIP/GLP-1 medicine.

Do not simply stop the medicine according to advice found online.

Different patients and procedures may require different plans.

Follow the treating team’s instructions.

Can I use these medicines during pregnancy?

No weight-loss treatment should continue during pregnancy.

GLP-1 medicines are not recommended during pregnancy.

If pregnancy is planned, discuss the medicine with your prescriber before trying to conceive.

The timing for stopping treatment before pregnancy depends on the specific medicine.

Tirzepatide and the contraceptive pill

This deserves a specific mention.

The TGA advises that reduced effectiveness of oral hormonal contraception cannot be excluded with tirzepatide.

If you use the contraceptive pill while taking tirzepatide, add a barrier method or switch to a non-oral method for:

• 4 weeks after starting tirzepatide; and
• 4 weeks after every dose increase.

This is particularly important during dose escalation.

Can my other medicines need changing?

Yes.

If you have type 2 diabetes, improved weight and blood glucose may mean existing diabetes medicines need adjustment.

The risk of hypoglycaemia is particularly important if incretin medicines are combined with medicines that can themselves cause low glucose.

The same principle applies to blood-pressure treatment.

Substantial weight loss can reduce blood pressure.

Symptoms such as:

• light-headedness;
• postural dizziness;
• faintness

may mean your antihypertensive treatment needs review.

Successful weight loss can change the rest of your medication requirements.

What happens when weight loss slows?

Almost everyone’s weight-loss curve eventually flattens.

That is normal.

A plateau does not automatically mean:

“The medicine has stopped working.”

Ask instead:

• How much weight have I lost overall?
• Have my health markers improved?
• Is my appetite reasonably controlled?
• Am I maintaining strength and activity?
• Is the treatment still worth its cost and side effects?

Sometimes stability after substantial weight loss is itself a successful outcome.

What happens if I stop?

This is one of the most important conversations to have before treatment begins.

Weight regain is common after GLP-1 or GIP/GLP-1 treatment is stopped.

This does not mean the medicine has permanently “damaged your metabolism”.

It means the biological drivers of weight can return when the medicine is removed.

Obesity is often a chronic relapsing condition.

Does this mean long-term treatment?

For many people, it may.

That does not necessarily mean taking the same medicine at the same dose forever.

Some people may:

• continue long term;
• reduce treatment;
• change medicines;
• stop with close follow-up;
• maintain some weight loss through lifestyle measures.

GLP-1 medicines have accumulated considerable clinical experience, particularly in diabetes, but modern obesity treatment may involve many years of therapy.

Long-term treatment therefore still needs regular review of:

• benefit;
• side effects;
• nutrition;
• muscle and function;
• other medicines;
• pregnancy plans;
• cost;
• whether the indication still makes sense.

The key is having a maintenance strategy, not simply a weight-loss strategy.

What about counterfeit or online products?

This is increasingly important.

In March 2026, the TGA warned Australians about counterfeit products claiming to contain medicines such as semaglutide, tirzepatide or liraglutide.

These products may contain:

• incorrect ingredients;
• no genuine active ingredient;
• incorrect doses;
• contamination;
• unsafe or misleading packaging.

GLP-1 and GIP/GLP-1 medicines are prescription medicines in Australia.

Use legitimate medical and pharmacy pathways rather than buying unregulated products through social media or overseas websites.

Are these medicines “cheating”?

No.

Obesity involves biological mechanisms that regulate appetite, energy balance and weight regain.

Medication does not remove the need for healthy behaviour.

It can make healthy behaviour more achievable.

We do not describe blood-pressure treatment as cheating because lifestyle changes might also help blood pressure.

The real question is whether treatment improves health safely.

Do they make healthy eating irrelevant?

Definitely not.

It is possible to lose weight while eating badly.

That is not the goal.

Use the period of reduced appetite to improve:

• food quality;
• portion size;
• protein intake;
• fibre;
• vegetables;
• hydration.

The medicine should support a healthier eating pattern rather than simply reduce the amount of an unhealthy one.

What should my GP monitor?

Follow-up should be individualised, but useful things to review include:

• weight and waist;
• blood pressure;
• blood glucose where relevant;
• gastrointestinal side effects;
• hydration;
• nutrition;
• protein intake;
• physical activity;
• strength;
• mood;
• other medicines;
• whether treatment remains affordable.

There should also be periodic reassessment of:

“Is this still improving health enough to justify continuing?”

A common misconception

MYTH: If I am not losing weight every week, the medicine has stopped working.

REALITY: Weight loss is not linear.

Plateaus are normal.

The important outcome is the longer-term trend and whether:

• health;
• function;
• appetite;
• metabolic risk

are improving.

Another common misconception

MYTH: Once I reach my goal weight, I can stop and my appetite will stay permanently reset.

REALITY: For many people, appetite increases and weight regain occurs after medication is stopped.

That is why maintenance needs to be discussed before the goal weight is reached.

And another

MYTH: The strongest dose is the best dose.

REALITY: The best dose is the one that provides a useful balance of:

• benefit;
• nutrition;
• side effects;
• function;
• sustainability.

More is not automatically better.

The question I would ask

After someone has been on treatment for several months, I would ask:

“What has improved apart from the number on the scales?”

Maybe the answer is:

• my HbA1c;
• my blood pressure;
• my sleep;
• my fatty liver;
• my knees;
• my ability to exercise;
• my energy;
• my cardiovascular risk.

Those are the outcomes that turn weight-loss treatment into health treatment.

The bottom line

GLP-1 and GIP/GLP-1 medicines have transformed obesity treatment.

For the right patient, they can produce substantial weight loss and may improve important obesity-related diseases.

But successful treatment involves more than prescribing an injection.

It requires attention to:

• gastrointestinal side effects;
• nutrition;
• muscle preservation;
• pregnancy;
• contraception;
• surgery and anaesthesia;
• rare but important safety warnings;
• other medicines;
• long-term affordability;
• what happens if treatment stops.

These are still prescription medicines that require proper medical supervision.

The goal is not:

“How quickly can I lose weight?”

It is:

“How can I use this treatment to improve my health in a way I can realistically sustain?”

Related Q Guides

• Weight-Loss Medicines: Who They Help, Who They Don’t and What to Expect
• Snoring, Tired and Foggy? Could It Be Sleep Apnoea?
• Fatty Liver: What Your Results Mean and What You Can Do