Tirzepatide
A weekly injection that copies two gut hormones controlling blood sugar and appetite. Used for type 2 diabetes, weight management and sleep apnoea with obesity. Powerful, and fully private.
Quick answer: Mounjaro (tirzepatide) most commonly causes nausea, diarrhoea and less appetite, plus vomiting, constipation and tummy pain at weight-loss doses. These are worst in the first weeks and after each dose increase, and usually settle. It can make the contraceptive pill less effective, so add condoms or use a non-pill method. Get urgent help for severe tummy pain that won’t settle.
At a glance
- For
- Type 2 diabetes; weight management; moderate to severe sleep apnoea with obesity
- Works
- Weight: about 15–21% of body weight lost on average over 72 weeks, depending on dose (about 3% on a dummy treatment). Diabetes: HbA1c falls by about 2%. Sleep apnoea: breathing pauses roughly halved
- Cost
- Not on the PBS for any use (October 2026). Private, about $280–690 a month, rising with dose
- Kicks in
- Appetite drops within weeks; dose stepped up every 4 weeks; weight loss builds over about 18 months
- Taken for
- Long term: weight usually returns after stopping
- Watch for
- Nausea, diarrhoea, vomiting, constipation, tummy pain, less appetite
On the pill? For 4 weeks after starting and after every dose step, add condoms or switch to a non-pill method. Mounjaro can make the pill less reliable, and surprise pregnancies are a real plot twist, not an internet myth.
Brand names
- Mounjaro (weekly injection pen)
How it works
Tirzepatide acts on two hormone receptors, GIP and GLP-1, boosting insulin when blood sugar is high, slowing the stomach and reducing appetite. Hitting both is thought to explain its bigger effect on weight.
Used for
- Type 2 diabetes, alongside diet and exercise
- Weight management in people with obesity, or overweight with a weight-related condition, alongside diet and activity
- Moderate to severe obstructive sleep apnoea in adults with obesity
Side effects
Most common: nausea, diarrhoea and less appetite, plus vomiting, constipation and tummy pain at weight-loss doses. These are worst in the first weeks and after each dose increase, and usually settle. Indigestion, burping, hair thinning and injection-site reactions are also common.
Full side-effect list (from the product information)
How often, from the official product information. Bold = serious.
Very common more than 1 in 10
- Nausea
- Diarrhoea
- Vomiting, constipation and tummy pain, especially at weight-loss doses
- Less appetite
- Low blood sugar, if also on insulin or a sulfonylurea
Common 1 in 10 to 1 in 100
- Allergic reactions such as rash or itch
- Dizziness
- Low blood pressure
- Indigestion, reflux, burping, wind or bloating
- Gallstones or gallbladder inflammation
- Hair thinning
- Injection-site reactions
- Tiredness
- Faster heart rate
- Raised pancreatic enzymes on blood tests
Uncommon 1 in 100 to 1 in 1,000
- Pancreatitis (inflamed pancreas)
- Slower stomach emptying
- Altered taste or unusual skin sensations
- Injection-site pain
Rare 1 in 1,000 to 1 in 10,000
- Anaphylaxis (severe allergic reaction)
- Angioedema (swelling of the face, lips or throat)
Get help urgently if
- Severe tummy pain that won’t settle, sometimes going through to the back (possible pancreatitis)
- Pain under the right ribs, fever or yellow skin (possible gallstones)
- Vomiting or diarrhoea so bad you can’t keep fluids down (risk of dehydration and kidney problems)
- Swelling of the face or throat, or trouble breathing
- Shakiness, sweating or confusion if you also take insulin or a sulfonylurea (low blood sugar)
Good to know
- Can make the contraceptive pill less effective. Use a non-pill method or condoms for 4 weeks after starting and after each dose increase.
- Not for use in pregnancy. Stop at least 1 month before trying to get pregnant.
- Not suitable with a personal or family history of medullary thyroid cancer or MEN2.
- Tell your doctor before any surgery or anaesthetic. Use only TGA-approved products from a pharmacy.
Common questions
What is Mounjaro used for?
Type 2 diabetes, weight management, and moderate to severe obstructive sleep apnoea in adults with obesity.
Is Mounjaro on the PBS?
No, not for any use as of October 2026. The PBAC recommended it for type 2 diabetes in March 2026, but the company didn’t proceed with listing. Private scripts cost roughly $280 to $690 a month, depending on dose.
Does Mounjaro affect the contraceptive pill?
It can make the pill less effective. Use a non-pill method or condoms for 4 weeks after starting and after each dose increase.
What are the common side effects of tirzepatide?
Nausea, diarrhoea and less appetite are very common, and vomiting, constipation and tummy pain especially at weight-loss doses.
Is Mounjaro the same as tirzepatide?
Yes. Mounjaro is a brand name for tirzepatide, used in Australia and many other countries. In the US, tirzepatide for weight management is also sold as Zepbound. Same medicine, different label.
Information only. Not a recommendation or endorsement of any product. Whether a medicine suits you depends on your health and other medicines, so talk to your doctor or pharmacist. In an emergency, call 000 (Australia) or your local emergency number. From a mobile, 112 works in most countries.
More information
- newsGP: Mounjaro approved for sleep apnoea
- TGA: Mounjaro public assessment report
- SURMOUNT-1 trial: Tirzepatide for obesity (NEJM)
- PBS: Tirzepatide listing status
- TGA: Updated contraception advice for Mounjaro
- newsGP: Mounjaro manufacturer rejects PBS recommendation (April 2026)
- AusDoc: Tirzepatide not listed on the PBS (April 2026)
maladywise.com/medicines/tirzepatide/