Ozempic vs Mounjaro (Semaglutide vs Tirzepatide)

Short answer: Both are weekly injections that cut appetite and lower blood sugar. Tirzepatide (Mounjaro) acts on two gut hormones, semaglutide (Ozempic, Wegovy) on one. In the only head-to-head weight trial, people lost about 20% of their weight on tirzepatide versus 14% on semaglutide. Side effects are similar. In Australia, only Ozempic is PBS-subsidised, for type 2 diabetes.

Semaglutide (Ozempic, Wegovy)

Copies GLP-1, one gut hormone
Ozempic: type 2 diabetes. Wegovy: weight management (also as a daily tablet)
Proven to cut heart attacks and strokes in people with heart disease and excess weight
Ozempic is on the PBS for type 2 diabetes only

Tirzepatide (Mounjaro)

Copies two gut hormones, GLP-1 and GIP
One brand in Australia for type 2 diabetes, weight management and sleep apnoea with obesity
More weight loss in the head-to-head trial
Not on the PBS for any use

How they work

Both mimic hormones your gut releases after eating. They boost insulin when blood sugar is high, slow stomach emptying and signal fullness to the brain, so people eat less.
Tirzepatide also activates the GIP receptor. That’s thought to explain part of its extra effect, though the details are still being worked out.
Both are once-weekly injections started at a low dose and stepped up every 4 weeks to limit side effects. Your doctor sets the dose.

Weight loss: the head-to-head trial

SURMOUNT-5 (published 2025) compared the two directly in 751 adults with obesity but without diabetes, for 72 weeks, at the highest dose each person could tolerate.
Average weight loss: 20.2% with tirzepatide versus 13.7% with semaglutide. Waist size fell by 18.4 cm versus 13.0 cm.
More people on tirzepatide reached 10%, 15%, 20% and 25% weight loss.
Caveats: the trial was open-label (people knew which drug they had) and funded by the maker of tirzepatide. It used semaglutide at the Wegovy dose (2.4 mg), higher than Ozempic’s doses.
Weight usually comes back after stopping either medicine. A year after stopping semaglutide in the STEP 1 trial, people had regained about two-thirds of the weight they’d lost.

Type 2 diabetes

In SURPASS-2 (40 weeks, 1,879 adults), HbA1c fell by 2.0 to 2.3 percentage points on tirzepatide versus 1.9 on semaglutide 1 mg. Tirzepatide also gave 1.9 to 5.5 kg more weight loss, depending on dose.
Both lower blood sugar without causing hypos on their own. Hypos can happen if they’re combined with insulin or a sulfonylurea.

Heart and other benefits

Semaglutide: in SELECT, 17,604 people with heart disease and overweight or obesity (no diabetes) had 20% fewer heart attacks, strokes or heart deaths over about 3 years than with placebo.
Tirzepatide: in SURPASS-CVOT, in people with type 2 diabetes and heart disease, it was at least as good as dulaglutide (another GLP-1 medicine with proven heart benefit): 12.2% versus 13.1% had a heart attack, stroke or heart death. That wasn’t enough to prove it better.
Tirzepatide is also TGA-approved for moderate to severe obstructive sleep apnoea in adults with obesity.

Side effects

Much the same for both: nausea, diarrhoea, vomiting, constipation and reflux, mostly mild to moderate and mainly while the dose is being increased.
Less common but serious for both: pancreatitis, gallstones, and dehydration from vomiting that can affect the kidneys.
Neither is for use in pregnancy or breastfeeding, or with a personal or family history of medullary thyroid cancer or MEN2.
Tirzepatide can make the contraceptive pill less reliable, especially when starting and after dose increases, so a backup method such as condoms is advised.
Tell your anaesthetist before any surgery or procedure: both slow stomach emptying.

Cost and PBS in Australia (November 2026)

Ozempic is PBS-subsidised for type 2 diabetes only ($25 a script, or $7.70 with a concession card). Using it for weight loss alone is off-label and needs a private script.
Wegovy was recommended by the PBAC for adults with obesity and established heart disease in November 2025, but as of 1 November 2026 it isn’t yet listed. Until then it’s private.
Mounjaro isn’t on the PBS. The PBAC recommended it for type 2 diabetes in March 2026, but the company didn’t proceed with listing. Private scripts cost several hundred dollars a month, rising with dose.
Only use TGA-approved products from a pharmacy. Compounded or online “copies” aren’t approved.

Which is right for you?

If you have type 2 diabetes and cost matters, PBS-subsidised Ozempic is often the starting point.
If you have heart disease and excess weight, semaglutide has direct evidence of fewer heart attacks and strokes.
If the main goal is maximum weight loss and cost isn’t a barrier, tirzepatide produced more in the head-to-head trial.
Either works best alongside changes to eating, activity and sleep, and both are usually long term. Talk it through with your GP.

Common questions

Is Mounjaro stronger than Ozempic?

For weight loss, yes on average. In the SURMOUNT-5 head-to-head trial, people lost about 20% of body weight on tirzepatide (Mounjaro) versus about 14% on semaglutide at the Wegovy dose, which is higher than Ozempic’s. Individual results vary a lot.

Is Mounjaro on the PBS?

No, not for any use as of November 2026. The PBAC recommended it for type 2 diabetes in March 2026, but the company didn’t proceed with listing. Ozempic is PBS-subsidised for type 2 diabetes only.

Which has fewer side effects, Ozempic or Mounjaro?

They’re similar. Both mainly cause nausea, diarrhoea, vomiting and constipation, mostly while the dose is going up. Rates in head-to-head trials were close.

Can I switch from Ozempic to Mounjaro?

Yes, people do switch, but only with your doctor’s guidance. The new medicine usually starts at a lower dose and is stepped up again, and you shouldn’t take both together.

Is Wegovy the same as Ozempic?

Both contain semaglutide. Ozempic is approved for type 2 diabetes and Wegovy for weight management, at a higher top dose. A daily Wegovy tablet is also TGA-approved.

Sources

Reviewed 8 November 2026. General education, not personal medical advice. Talk to your GP or pharmacist about what suits you.