Mounjaro is a once-weekly prescription injection containing tirzepatide. It acts on two hormone pathways, GIP and GLP-1, to reduce appetite and food intake. In New Zealand, Mounjaro is approved for chronic weight management in adults with obesity, or in some adults who are overweight and have a weight-related health condition.
Clinical trials have shown average weight loss of approximately 15% to 21% over 72 weeks, depending on the dose used. Individual results vary, and medication works best as part of a structured, long-term approach to obesity treatment.
At Southern Weight Loss, we can assess whether Mounjaro is appropriate, discuss alternatives such as Wegovy, and help develop a weight management plan based on health, previous treatment, goals and long-term sustainability.
What is Mounjaro?
Mounjaro is the brand name for tirzepatide, a prescription medication given by injection once a week.
Tirzepatide is sometimes grouped with GLP-1 weight loss medications, but it works slightly differently. It activates both:
- GIP, or glucose-dependent insulinotropic polypeptide receptors
- GLP-1, or glucagon-like peptide-1 receptors
These hormones are involved in appetite, food intake and glucose regulation.
Mounjaro was initially developed as a treatment for type 2 diabetes and is now also approved in New Zealand for chronic weight management in eligible adults.
It should be used alongside appropriate nutrition, physical activity and ongoing medical support rather than viewed as a stand-alone or short-term weight loss treatment.
How does Mounjaro work for weight loss?
Mounjaro acts on biological pathways involved in appetite and energy regulation.
It can:
- reduce hunger
- increase feelings of fullness after eating
- reduce food intake
- make it easier to eat smaller portions
- reduce some of the persistent thoughts about food that can make weight management difficult
- improve glucose regulation in people with type 2 diabetes or insulin resistance
Mounjaro also delays gastric emptying, particularly when treatment is first started.
The important point is that tirzepatide does not simply rely on someone having more willpower. It changes some of the biological signals that influence hunger and food intake.
How much weight can people lose with Mounjaro?
Mounjaro is one of the most effective weight loss medications currently available.
In the large SURMOUNT-1 clinical trial, adults with obesity or overweight without diabetes were treated for 72 weeks.
Average weight reductions were approximately:
| Dose | Average weight reduction (72 weeks) |
|---|---|
| 5 mg Mounjaro | 15.0% |
| 10 mg Mounjaro | 19.5% |
| 15 mg Mounjaro | 20.9% |
| Placebo | 3.1% |
Some people lost considerably more, while others lost less or did not achieve a clinically meaningful response.
These figures are averages from a clinical trial and should not be interpreted as a prediction or guarantee of individual weight loss.
How well someone responds can be affected by several factors, including dose tolerance, starting weight, other medical conditions, medications, nutrition, activity and individual biology.
Who can use Mounjaro for weight loss in New Zealand?
Mounjaro is approved in New Zealand for chronic weight management, including weight loss and weight maintenance, alongside a reduced-calorie diet and increased physical activity.
It can be considered in adults with:
- A BMI of 30 kg/m² or greater
- or a BMI of 27 kg/m² to under 30 kg/m² with at least one weight-related medical condition
Examples include:
- high blood pressure
- abnormal cholesterol
- obstructive sleep apnoea
- cardiovascular disease
- prediabetes
- type 2 diabetes
Meeting these criteria does not automatically mean Mounjaro is the right treatment.
A medical assessment should consider previous attempts at weight management, current medications, medical history, treatment goals, possible contraindications, side effects and the ability to continue treatment over the longer term.
What dose of Mounjaro is used?
Mounjaro is taken once a week.
The usual starting dose is:
- Weeks 1 to 4: 2.5 mg once weekly
- After four weeks: 5 mg once weekly
If additional treatment effect is required and the medication is being tolerated, the dose can subsequently be increased in 2.5 mg steps after at least four weeks on the current dose.
Available doses include: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg.
The recommended maintenance doses are 5 mg, 10 mg or 15 mg weekly. The maximum recommended dose is 15 mg once weekly.
There is no requirement for everyone to reach the maximum dose. Dose decisions should take into account both effectiveness and tolerability.
Does everyone need to increase to 15 mg?
No.
The aim is not simply to reach the highest dose.
Some people achieve good appetite control and clinically meaningful weight loss at a lower dose. Others may benefit from gradual escalation.
Increasing the dose too quickly can also increase gastrointestinal side effects.
Treatment should therefore be individualised rather than following a race to the maximum dose.
Mounjaro vs Wegovy: what is the difference?
Both Mounjaro and Wegovy are once-weekly prescription injections used for chronic weight management, but they are different medications.
Wegovy contains semaglutide and acts on the GLP-1 receptor. Mounjaro contains tirzepatide and acts on both GIP and GLP-1 receptors. Both reduce appetite and food intake.
In a direct 72-week clinical trial comparing tirzepatide with semaglutide in adults with obesity without diabetes, average weight loss was greater with tirzepatide.
However, this does not mean Mounjaro is automatically the right medication for every person.
Choice of treatment should take into account:
- medical history
- previous GLP-1 treatment
- response to treatment
- side effects
- other medications
- diabetes and other weight-related conditions
- affordability
- ability to remain on treatment
- personal treatment preferences
For some people, Wegovy may be appropriate. For others, Mounjaro may be a better option.
What are the side effects of Mounjaro?
The most frequently reported side effects are gastrointestinal.
These include:
- nausea
- diarrhoea
- constipation
- vomiting
- abdominal discomfort or pain
- indigestion
- bloating
- reflux or burping
These symptoms are generally most noticeable when starting treatment or increasing the dose and often improve with time.
Other reported effects can include dizziness, fatigue, injection-site reactions and hair loss.
Less common but potentially important complications include pancreatitis, gallbladder disease and significant dehydration resulting from persistent vomiting or diarrhoea.
People using insulin or some diabetes medications may also be at increased risk of hypoglycaemia and may require adjustment of their diabetes treatment.
Severe or persistent symptoms should be medically assessed rather than simply tolerated.
Who may need extra caution with Mounjaro?
Mounjaro is not appropriate for everyone.
Particular consideration is required for people with:
- previous pancreatitis
- severe gastrointestinal disease or severe gastroparesis
- significant kidney or liver disease
- diabetes treated with insulin or sulfonylureas
- diabetic retinopathy
- pregnancy or plans for pregnancy
- medications where changes in absorption could be important
Tirzepatide delays gastric emptying. Anyone undergoing an operation, endoscopy or procedure requiring sedation or anaesthesia should tell their treating team that they are taking Mounjaro.
Mounjaro should not normally be taken at the same time as another GLP-1 receptor agonist.
Mounjaro and contraception
This is particularly important for women using an oral contraceptive pill.
Because tirzepatide delays gastric emptying, it may affect the absorption and effectiveness of oral hormonal contraceptives.
The New Zealand prescribing information advises people using oral hormonal contraception to either use a non-oral contraceptive method or add a barrier method for four weeks after starting Mounjaro and for four weeks after each increase in dose.
Mounjaro should not be used during pregnancy.
Anyone who is pregnant, planning pregnancy or using oral contraception should discuss this with their treating clinician before starting treatment.
How much does Mounjaro cost in New Zealand?
Mounjaro is currently not publicly funded by Pharmac for weight loss, so patients generally pay the pharmacy cost themselves.
The price varies considerably according to the dose and pharmacy.
As a guide, retail pricing in New Zealand in August 2026 ranges from approximately $430 to $875 for a four-dose KwikPen, depending on the strength.
Because prices can change, we recommend checking the current cost with the dispensing pharmacy before starting treatment.
Pricing checked August 2026. Pharmacy prices may change.
How long do people stay on Mounjaro?
Mounjaro should generally be thought of as treatment for a chronic disease, rather than a short course of medication.
There is no universal point at which everyone should stop.
In a clinical trial examining withdrawal of tirzepatide, people who stopped treatment regained a significant proportion of the weight they had lost, while people who continued treatment generally maintained or increased their weight loss.
That does not necessarily mean every person needs Mounjaro indefinitely.
Long-term treatment decisions should consider:
- effectiveness
- side effects
- health improvements
- cost
- changing medical circumstances
- patient preference
- whether another treatment strategy would be more sustainable
These decisions are best made as part of ongoing weight management rather than stopping medication simply because a target weight has been reached.
What happens if Mounjaro does not work?
Not everyone responds to weight loss medication in the same way.
For some people Mounjaro produces substantial weight loss. Others have a more modest response, cannot tolerate an effective dose, regain weight after treatment or find the long-term cost difficult to sustain.
If medication is not producing the expected benefit, the answer is not necessarily to keep escalating indefinitely.
It may be appropriate to review:
- the dose
- nutrition
- protein intake
- physical activity
- other medications
- sleep
- underlying medical conditions
- whether another weight loss medication is appropriate
- whether bariatric surgery should be considered
Medication and bariatric surgery are not competing treatments. They are different tools for treating obesity, and the most appropriate option depends on the individual.
Mounjaro after bariatric surgery
Weight loss medications such as Mounjaro may sometimes have a role after bariatric surgery.
Examples include people experiencing:
- significant weight regain
- inadequate weight loss
- a persistent weight plateau
- recurrence of appetite or food noise
However, post-bariatric patients need individual assessment before starting medication.
Nutrition, vitamin status, the original operation, anatomy, eating patterns and possible surgical causes of weight regain should be considered rather than treating the number on the scales alone.
A medically supported approach to Mounjaro
Weight loss medication works best when the medication is only one part of the treatment.
At Southern Weight Loss, we take a broader view of obesity management.
An assessment can include:
- medical history and current health
- previous weight loss attempts
- previous GLP-1 or weight loss medication use
- appetite and eating patterns
- weight-related medical conditions
- medication options
- side-effect management
- nutrition
- longer-term treatment planning
- whether bariatric surgery should also be considered
The goal is not simply to write a prescription.
It is to find a treatment strategy that is medically appropriate, effective and sustainable.
Start the conversation
If Mounjaro, Wegovy or another approach to weight management is being considered, Southern Weight Loss can help assess the available options.
No GP referral is required.
Frequently asked questions about Mounjaro
Is Mounjaro available in New Zealand?
Yes. Mounjaro containing tirzepatide is available as a prescription medicine in New Zealand and is approved for chronic weight management in eligible adults.
Is Mounjaro approved for weight loss in New Zealand?
Yes. Mounjaro is approved for chronic weight management in adults with a BMI of 30 kg/m² or above, or a BMI of 27 kg/m² to under 30 kg/m² with at least one weight-related medical condition.
Is Mounjaro funded in New Zealand?
No. Mounjaro is currently not Pharmac-funded for weight loss. Patients generally need to pay the full pharmacy cost themselves.
How much does Mounjaro cost in NZ?
The price depends on the strength and pharmacy. As of August 2026, advertised New Zealand pharmacy prices are approximately $430 to $875 for a four-dose KwikPen. Prices can change, so current pharmacy pricing should be checked.
How much weight can I lose with Mounjaro?
In a major 72-week clinical trial, average weight loss ranged from approximately 15% with 5 mg tirzepatide to around 21% with 15 mg. Results vary significantly between individuals and cannot be guaranteed.
Is Mounjaro better than Wegovy?
In a direct clinical trial, tirzepatide produced greater average weight loss than semaglutide over 72 weeks. However, effectiveness is only one consideration. Side effects, medical history, cost, previous treatment and individual response all matter when choosing between Mounjaro and Wegovy.
Is Mounjaro the same as Ozempic?
No. Mounjaro contains tirzepatide and acts on both GIP and GLP-1 receptors. Ozempic contains semaglutide and acts on the GLP-1 receptor. They are different medicines.
How often is Mounjaro injected?
Mounjaro is injected under the skin once a week.
What dose of Mounjaro do you start with?
The usual starting dose is 2.5 mg once weekly for four weeks, followed by 5 mg once weekly. Further dose increases can be considered at intervals of at least four weeks according to treatment response and side effects.
Do I have to take Mounjaro forever?
Not necessarily, but obesity is a chronic condition and weight regain is common after weight loss medication is stopped. Long-term treatment should therefore be discussed from the beginning rather than assuming Mounjaro will be used only until a target weight is reached.
What are the most common Mounjaro side effects?
The most common side effects are nausea, diarrhoea, constipation and vomiting. They tend to occur most often when treatment is started or the dose is increased and frequently improve over time.
Can I use Mounjaro if I take the contraceptive pill?
Extra contraception may be required. Tirzepatide can affect absorption of oral hormonal contraceptives. New Zealand prescribing information recommends using a non-oral contraceptive method or adding a barrier method for four weeks after starting Mounjaro and for four weeks after each dose increase.
Can Mounjaro be used after weight loss surgery?
Sometimes. GLP-1 and GIP/GLP-1 medications can have a role in managing weight regain or inadequate weight loss after bariatric surgery, but nutritional, behavioural and surgical causes should also be assessed.
Do I need a GP referral to discuss Mounjaro with Southern Weight Loss?
No. Patients can contact Southern Weight Loss directly for an assessment.
Clinical references
Medically reviewed by Mr Mark Grant, Bariatric Surgeon. Last reviewed: August 2026.
- New Zealand Medsafe Mounjaro Data Sheet, current version
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine.
- Aronne LJ et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity. JAMA.
- Tirzepatide compared with semaglutide for obesity, New England Journal of Medicine.
- Pharmac New Zealand funding information.
External references
- Medsafe New Zealand Mounjaro data sheet
- Pharmac information about funding of Mounjaro and Wegovy
- Major peer-reviewed tirzepatide clinical trial evidence
Considering Mounjaro for weight loss?
Choosing a weight loss medication involves more than choosing a brand or a dose.
Southern Weight Loss can assess whether Mounjaro, Wegovy or another treatment approach is appropriate and help build a plan around long-term health rather than short-term weight loss alone.
No GP referral is required.