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What is Mounjaro used for? A guide to the prescription medication

Approved for use in the UK for adults with obesity or type 2 diabetes, Mounjaro has gained attention as a medicated weight treatment option in recent years. But what drug is Mounjaro? Here's everything you need to know.

By Rebecca Roberts Reviewed by Dr David Porter | Last updated Oct 23, 2025

This content is for information only and doesn't replace medical advice. Always consult your GP before starting weight loss injections to discuss suitability, risks, and monitoring. Seek medical attention if you experience concerning symptoms.
A close up of a persons hands holding Mounjaro

Mounjaro is a prescription weight-loss and diabetes injection that contains tirzepatide - a drug used to help regulate blood sugar and reduce appetite. It’s part of a class of medications sometimes called GLP-1 weight-loss injections.

Unlike medicines that target a single hormone (such as Ozempic, which only acts on GLP-1), tirzepatide targets two: GLP-1 and GIP. Together, they help regulate blood sugar and reduce appetite. It isn’t insulin, and you can only get it on prescription after a proper medical assessment.

Worried about the price increase of Mounjaro?

You’re not the only one. Mumsnet is the go-to destination for weight loss injection discussions, so if you have any questions about Mounjaro for weight management and the price increases, head to our dedicated Talk board. 

Visit our weight loss injections board

This guide covers

What is in Mounjaro and how does it work?

Mounjaro contains tirzepatide, a prescription medication originally designed to treat type 2 diabetes that's now also licensed for weight management.

Unlike other weight loss treatments, tirzepatide works as a dual-action medication that targets two key hormone systems in your body.

“Whereas GLP-1 medications target one hormone, tirzepatide mimics the effects of two hormones that can help manage blood sugar levels," explains Dr Daniel Atkinson, clinical lead at Treated.com. “GIP stimulates the release of insulin after meals, and GLP-1 is involved in regulating your appetite by telling you when you’ve eaten enough. Both hormones also influence other processes involved in blood sugar regulation.”

Together, these actions help reduce appetite, improve blood sugar control and support sustainable weight loss. Learn more about how GLP-1 weight loss injections work.

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What is tirzepatide?

Tirzepatide is the active ingredient in Mounjaro. It's a dual GLP-1 and GIP receptor agonist, meaning it mimics two naturally occurring hormones in your body that are released when you eat.

These hormones work together as part of what scientists call the "incretin system" - your body's natural post-meal management system that controls appetite, blood sugar and digestion.

Related: What is Ozempic and can it be used for weight loss?

What drug class is Mounjaro in?

Mounjaro contains tirzepatide, which is in the GIP/GLP-1 receptor agonist drug class.

Is Mounjaro licensed for weight management?

The Medicines and Healthcare products Regulatory Agency (MHRA) has approved tirzepatide to treat both type 2 diabetes as well as weight management alongside a reduced calorie diet and exercise in people with obesity, or people who are overweight with weight-related health problems. 

Find out more from GOV.UK

How Mounjaro helps with weight loss

Mounjaro supports weight loss by working in several complementary ways:

Through GLP-1 (glucagon-like peptide-1), your body's natural 'meal manager':

  • Slows stomach emptying so you feel fuller for longer

  • Signals to your brain that you've had enough to eat, reducing appetite

  • Tells the pancreas to release insulin when blood sugar rises

  • Blocks glucagon, preventing your liver from releasing unnecessary sugar into your bloodstream

Through GIP (glucose-dependent insulinotropic polypeptide), GLP-1's complementary partner:

  • Stimulates insulin release when blood sugar is elevated

  • Further slows how quickly food leaves your stomach

  • Helps direct fat storage into fat cells rather than allowing it to circulate in your bloodstream

"Tirzepatide works by increasing insulin production, reducing glucose production and slowing down digestion," adds Dr Atkinson. "This combination of effects helps manage both blood sugar levels and appetite."

Mounjaro is administered as a once-weekly injection using a pre-filled pen that you can use yourself at home.

A woman smiles at her phone

Whether you're accessing Mounjaro online or in person via your GP, being transparent about your medical history is vital

What drug is Mounjaro?

As mentioned above, Mounjaro is a prescription medication containing tirzepatide. It's classified as a GLP-1 and GIP receptor agonist - essentially, it's a medication that copies two natural hormones in your body to help control your blood sugar and reduce your appetite.

Mounjaro was first created to treat diabetes, but doctors noticed people were losing significant amounts of weight while taking it. After more research and trials, it was approved for weight management too.

The medication tackles several things at once that make it hard to lose weight – it helps control your appetite, manages your blood sugar better and slows down how quickly your stomach empties after eating.

How Mounjaro helps with weight loss

It works in ways that go beyond just making you feel less hungry, including:

Turning down the 'food noise'

One of the biggest changes people notice on Mounjaro is what many call "food noise" going away. Food noise is that constant mental chatter about food - thinking about your next meal, battling cravings or feeling like food is always on your mind.

When Mounjaro mimics your body's natural GLP-1 hormone, it helps get your appetite signals back to normal. This makes it easier to:

  • Feel satisfied after eating less food

  • Go hours between meals without feeling starving

  • Make better food choices instead of grabbing whatever's nearby because you're desperate

  • Stop eating in response to stress or emotions

Helping you lose weight and keep it off

Beyond quieting food noise, Mounjaro's double-action approach helps by:

  • Keeping blood sugar steady: No more energy crashes that make you desperate for a snack

  • Slowing down digestion: You stay fuller for much longer after eating

  • Helping insulin work better: Your body becomes more efficient at using the food you eat

In studies, people taking Mounjaro lost between 15-22% of their starting weight over about a year and a half, depending on their dose. But everyone's different – some lose more, some less. And it works best when you're also making changes to what you eat and trying to move more.

Related: What happens when you stop taking weight loss drugs?

Is Mounjaro only for people with diabetes?

No - even though Mounjaro was made for type 2 diabetes first, you don't need to have diabetes to get it prescribed for weight loss. You do need to tick certain boxes healthwise, though.

When Mounjaro might be prescribed

Mounjaro is not a first-line treatment. It's prescribed when:

  • Other treatments for type 2 diabetes (like metformin) haven't worked

  • A person is referred to an NHS tier 3 or 4 weight management service

  • There's a clinical need to reduce weight to improve health outcomes

Dr Daniel stresses: "Weight loss injections are designed to be used for safe, effective weight loss in the long-term. I'd explain that weight loss treatments should never be prescribed for cosmetic purposes, or as a quick-fix means of losing weight. Mounjaro shouldn't be prescribed for either of these reasons."

Who shouldn't take it

Mounjaro isn't right for everyone. Doctors won't prescribe it if you:

  • Have type 1 diabetes

  • Have a personal or family history of certain types of thyroid cancer (medullary thyroid carcinoma)

  • Have a condition called multiple endocrine neoplasia syndrome type 2

  • Are pregnant or breastfeeding

If you're pregnant – or planning to conceive – and/or breastfeeding, taking tirzepatide is also not recommended.

"The data about how tirzepatide can affect the health of babies is limited," Dr Daniel explains, "but generally, weight loss treatments wouldn't be recommended for pregnant women because there hasn't been enough research into the potential effects they might have on a developing fetus."

Your doctor will look at your complete medical history, your current health, and your weight loss goals to figure out if Mounjaro is safe and suitable for you. They'll also check what other medications you're taking and talk through the possible risks and benefits based on your specific situation.

! Always read the Patient Information Leaflet and report any concerns via the MHRA Yellow Card Scheme.

What are the typical Mounjaro doses?

Mounjaro is taken as a once-weekly injection, with doses gradually increased over time under medical supervision. This stepped approach helps your body adjust to the medication and minimises potential side effects.

The treatment follows a carefully structured dosing schedule designed to find the right balance between effectiveness and tolerability for each individual.

Starting, maintenance and highest doses explained

Mounjaro treatment begins with a low dose that's increased progressively. Dr Daniel explains: “When used for weight loss, Mounjaro is usually prescribed at the starting dose of 2.5mg. 

“The titration dosing schedule means you usually change pens every four weeks. This approach helps your body adjust to tirzepatide, and can reduce the intensity of side effects.

“The recommended way to increase is by 2.5mg each month - starting with 2.5mg at month one and increasing to 15mg by month six, and then maintaining at this dose for as long as needed.

The standard dosing schedule:

  • Starting dose: 2.5mg once weekly for four weeks

  • Escalation: Increased by 2.5mg every four weeks, based on your response and tolerability

  • Available doses: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg

  • Maximum dose: 15mg once weekly - the highest approved dose of Mounjaro

Dr Daniel adds: “patients will need regular blood tests to monitor their blood sugar levels. For weight loss, it’s usually a case of checking how well the medication is working, and if side effects are manageable.” 

What is a maintenance dose?

Your maintenance dose is the level at which you achieve effective weight loss and blood sugar control with manageable side effects. For some people, this might be 5mg; for others, it could be 10mg or 15mg.

There's no one-size-fits-all maintenance dose – it's personalised to your individual response and medical needs.

What is the 'golden dose' people talk about?

If you've seen people on social media referring to Mounjaro's "golden dose," you might be wondering what this means.

Mounjaro injection pens are designed with presets for each one of your four doses in a month. There is extra medication in the pen, however, which is used for priming your needle before each use. You may come across some people accessing this extra "golden dose" so they can take a fifth dose out of their pen, but this is discouraged by several providers and is even impossible to do with the design of certain pens.

Drug interactions

Tirzepatide slows gastric emptying, which may affect how well some oral medicines are absorbed. This can be particularly relevant for medications such as oral contraceptives, anti-depressants or painkillers. If you take these, your doctor may recommend adjustments or alternative options.

Different dosages of Mounjaro injections

You don't need to race through to higher levels of Mounjaro if a lower dosage is working for you

What time of day is best to take Mounjaro?

You can inject Mounjaro at any time of day that works consistently for you - morning, afternoon or evening.

The medication works the same way regardless of when you take it. What matters most is that you're consistent with your day and time, but equally, don't be worried if you take it a few hours earlier or later than you normally would.

Practical tips:

  • Choose a day and time that fits your routine so you're less likely to forget

  • Many people prefer a day when they're typically at home and can relax afterward

  • Some choose a specific day (like "Mounjaro Monday") to make it memorable

  • Set a phone reminder for your injection day

The "best" time is simply the time that works best for your schedule and helps you maintain consistency.

Related: Ozempic vs Mounjaro vs Wegovy what's best for weight loss?

How is Mounjaro taken?

Mounjaro is injected once a week into the fatty layer under the skin. The pen used is called the KwikPen.

Dr Daniel explains: “You administer tirzepatide yourself, into your upper arm, thigh or abdomen. It’s what’s known as a subcutaneous injection; these are applied to the layer of fat just beneath your skin.”

Common injection sites are: 

  • Stomach (not too close to the belly button)

  • Thigh

  • Upper arm (if someone else gives the injection)

Rotate sites to reduce skin irritation and try to inject on the same day each week to keep the medication steady in your system.

How to store and handle your Mounjaro safely

Once you've started using your Mounjaro pen, you have two storage options.

Room temperature storage: Keep at normal room temperature up to 30°C, but it must be used within 30 days. Store in the original box and away from direct sunlight.

Refrigerator storage: Store between 2 to 8°C in your fridge with no time limit. Keep in the original packaging as well.

Choose whichever method works best for your routine. The key difference is that room temperature storage has a time limit, while refrigerated storage doesn't.

What happens if Mounjaro is not refrigerated?

If your Mounjaro pen is left out of your fridge for up to 30 days, it may begin to break down and lose its effectiveness. So, if you need to store your medicine for a long period, it's probably best to keep it in the fridge.

As mentioned above, the ideal storage is between 2 and 8°C in your fridge.

What are the most common side effects of Mounjaro?

Like most prescription medicines, tirzepatide can cause side effects. These are usually mild and ease as your body adjusts.

Digestive side effects

The most common side effects include: 

Dr Daniel notes: “Side effects like nausea, vomiting and diarrhoea are common when you start using Mounjaro. They should settle as you adjust to the medication, and won’t affect everyone in the same way.”

My advice would be to take the jab when you have a quiet couple of days in case of side effects. Eat small portions regularly and aim for protein with every meal.

catchingzzzeds

What is 'Mounjaro face'?

You may have seen discussions online about 'Mounjaro face', which is a genuine concern for many considering or taking weight loss medications.

'Mounjaro face' typically refers to:

  • Loss of facial volume in the cheeks, under-eyes and temples

  • More visible facial lines and wrinkles

  • Sagging skin around the jawline or neck

  • An overall more aged or gaunt appearance

The truth is, though, this isn't unique to Mounjaro. Significant weight loss from any method can affect facial volume. When you lose fat, you lose it everywhere, including your face. Rapid weight loss gives skin less time to adapt, making changes more noticeable - especially if you're over 30 to 35 when collagen production naturally slows.

[...] I am losing weight, feel much better about my health in general and so far have escaped all but very slight side effects [...]

PigglyWigglyOhYeah

When to speak to your doctor

Serious but less common side effects include pancreatitis (severe abdominal pain), gallbladder issues, hypoglycaemia (if used with insulin), and severe allergic reactions. Tirzepatide may also worsen diabetic retinopathy, particularly in patients who are also using insulin, so monitoring is advised.

! This is not a full list of side effects. You will get a full list of known side effects in the Patient Information Leaflet (PIL) that comes with your medication box. 

Related: Why am I so tired all the time? A guide to fatigue

Missing a Mounjaro dose

If you forget to administer your weekly injection and it’s been: 

  • Four days or less since you should have taken it, inject it as soon as you remember and take your next dose as usual on your scheduled day. 

  • More than four days since you should have taken it, skip your missed dose and take your next dose as usual on your scheduled day. 

Don’t inject a double dose to make up for a missed dose. This won’t make it more effective and can actually increase the risk of side effects. 

The minimum time between two Mounjaro doses must be at least three days. 

A view of Mounjaro's website on a screen

Remember significant weight loss from any method can cause side effects like 'Mounjaro face'

How long do you take Mounjaro for?

Mounjaro is designed for long-term use - there's no set end date. Treatment duration depends entirely on your individual circumstances, goals, and how well the medication works for you.

Typical Mounjaro treatment timelines

For type 2 diabetes: Many people continue Mounjaro indefinitely as part of their ongoing diabetes management, alongside diet and lifestyle measures.

For weight management: Most clinical trials studied Mounjaro between 36 and 72 weeks, but real-world use often extends beyond this. You might take it for:

  • 12 to 18 months minumum to achieve significant weight loss

  • Two years or longer to maintain results and establish lasting habits

  • Longer-term or indefinitely if stopping leads to weight regain

Can you stay on Mounjaro permanently?

There's no medical reason you can't take Mounjaro long-term if it continues to work for you and you're not experiencing problematic side effects. However, it's not intended as a lifelong solution for everyone.

Your doctor will regularly review whether you're still benefitting from treatment alongside any side effects or health changes you might have. They'll also examine your ability to maintain weight loss with lifestyle changes alone and also how cost-effective it is to continue treatment sustainably.

Related: What causes sulphur burps and how to stop them

What Mumsnet users say about Mounjaro

Mounjaro - or tirzepatide - has become a growing topic of discussion on our Talk boards, especially among users managing type 2 diabetes or accessing GLP-1/GIP-based medications through specialist weight management services. 

While individual experiences differ, a few consistent themes emerge across the discussions:*

Side effects are common - but often manageable: Digestive issues like nausea, bloating, sulphur burps and constipation are frequently mentioned. For many, these symptoms tend to ease over time or with dose adjustments.

Don't panic about side effects. I had read so many horror stories but mine were pretty mild to start off with and certainly not debilitating.

Wonderfulstuff

Emotional effects vary, but some see big benefits: Some users report initial anxiety or mood changes, while others say they notice a greater sense of calm after settling into the treatment. 

Caution around long-term risks and interactions: There are ongoing concerns about potential long-term side effects, particularly related to the pancreas or gallbladder. Users taking other medications (like antidepressants or pain relief) sometimes worry about how Mounjaro might affect absorption or interactions, too.

How well it would work [with] my T2 diabetes. That was primarily the reason the consultant put me on it and in 7 months my HBA1C has dropped from 93 to 51. Shocked and happy, the two stone weight loss has been a fabulous bonus.”

Kevinbaconsrealwife

Compared to other GLP-1 Drugs, Mounjaro often comes out ahead: Many users say they tolerate Mounjaro better than alternatives like Wegovy or Ozempic, particularly when it comes to side effects. However, personal responses vary.

Overall, Mumsnetters describe it as a useful tool rather than a cure-all, with the caveat that it doesn’t suit everyone.

How does Mounjaro compare to Ozempic and Wegovy?

Many people wonder what’s better, Ozempic or Mounjaro, or how Wegovy compares - while all three are GLP-1 medications, their active ingredients differ. Understanding the distinction can help you make an informed decision about your treatment.

The key difference? Single vs. dual action. Ozempic and Wegovy both contain the same active ingredient, semaglutide, which is a GLP-1 receptor agonist. They target one hormone system to help with appetite control and blood sugar regulation. The former isn't licensed in the UK for weight loss, however.

Mounjaro on the other hand contains tirzepatide, which is a dual GLP-1 and GIP receptor agonist. By targeting two hormone systems instead of one, it works through multiple complementary pathways.

In summary:

  • Ozempic: licensed for type 2 diabetes (though sometimes prescribed off-label for weight loss). Maximum dose: 2mg weekly.

  • Wegovy: licensed specifically for weight management. Contains the same drug as Ozempic but at higher doses. Maximum dose: 2.4mg weekly.

  • Mounjaro: licensed for both type 2 diabetes and weight management. The dual-action formulation. Maximum dose: 15mg weekly.

All three are taken as once-weekly injections and work best when combined with a balanced diet and regular physical activity.

Feature

Mounjaro

Ozempic

Wegovy

Active ingredient

Tirzepatide

Semaglutide

Semaglutide

Drug class

GIP/GLP-1 receptor agonist (dual action)

GLP-1 receptor agonist

GLP-1 receptor agonist

Primary use

Type 2 diabetes and weight loss

Type 2 diabetes

Weight loss

Administration

Weekly injection (subcutaneous)

Weekly injection (subcutaneous)

Weekly injection (subcutaneous)

Starting dose

2.5mg

0.25mg

0.25mg

Maintenance doses

5mg, 7.5mg, 10mg, 12.5mg, 15mg

0.5mg, 1mg, 2mg

0.5mg, 1mg, 1.7mg, 2.4mg

Want to switch from Mounjaro to Wegovy? Read our complete guide on switching from Mounjaro to Wegovy safely and effectively.

Who can get Mounjaro in the UK?

Mounjaro is available in the UK through both NHS and private prescription routes, though eligibility criteria apply. Access depends on your BMI, existing health conditions, and whether you're seeking treatment for type 2 diabetes or weight management.

NHS access criteria

Wondering what BMI is needed for Mounjaro? On the NHS, Mounjaro is primarily prescribed for type 2 diabetes management. For weight loss purposes, NHS eligibility typically requires:

  • BMI ≥ 35 with at least one weight-related health condition (such as high blood pressure, type 2 diabetes, or sleep apnoea), OR

  • BMI ≥ 30 in certain circumstances with clinical approval

NHS access remains limited due to supply constraints and NICE guidance. Your GP or specialist will assess whether you meet the criteria based on your individual circumstances.

Want to know more about NHS weight-loss treatment? Read our guide: Can you get weight-loss injections on the NHS?

NHS prescription costs

If you're prescribed Mounjaro through the NHS, you'll pay the standard NHS prescription charge of £9.90 per item in England. However, as mentioned, NHS access is currently limited due to supply constraints and strict eligibility criteria.

If you need multiple prescriptions or are on long-term treatment, you might benefit from a prescription prepayment certificate (PPC), which costs around £31.25 for three months or £111.60 for 12 months and covers unlimited prescriptions.

Is there a Mounjaro shortage in the UK?

Yes, supply has been an ongoing issue. Since late 2023, Mounjaro has faced intermittent shortages across the UK due to high global demand. This has affected both NHS and private supply chains. You can keep track of supply over on GOV.UK who share alerts, recalls and safety information related to medications.

Find drug alerts on GOV.UK

Private prescription options

Private prescriptions offer another route to access Mounjaro if you don't meet NHS criteria or prefer faster access. Private eligibility generally requires:

  • BMI ≥ 30, or

  • BMI ≥ 27 with weight-related health conditions

Private routes include:

  • Private GP consultations

  • Registered online healthcare providers

  • Specialist weight management clinics

  • High street and online pharmacies (with valid prescription)

Related: Hair loss in women, the causes and treatments that work

Private prescription costs

Private costs typically range from £150 to £300+ per month depending on dosage and provider.

  1. Starting doses (2.5mg-5mg): £150 to £200 per month

  2. Maintenance doses (7.5mg-12.5mg): £200 to £250 per month

  3. Maximum dose (15mg): £250 to £300+ per month

These prices typically include a medical consultation and assessment, the medication itself and ongoing monitoring and support.

A woman speaks to a male doctor

Make sure you speak to your doctor before starting or stopping any weight loss treatment

Who should you speak to about Mounjaro?

If you're considering tirzepatide, your first stop should be a healthcare professional: GP, diabetes specialist or weight management team. They will:

  • Review your medical history and BMI

  • Check other conditions and medicines you're on

  • Explain possible benefits and side effects

  • Decide if you meet NHS criteria or need a referral

  • Show you how to take it and monitor your progress

! Never start tirzepatide without a full medical assessment. Using it without proper checks could be dangerous, especially if you have conditions such as kidney disease, eye problems or a history of pancreatitis.

Dr Daniel says: "Weight loss treatments like Mounjaro can be effective, life-changing medications for some people.

"But they're only effective when used alongside a healthy diet and exercise plan - and these are habits people need to learn and practice before eventually stopping treatment, for the results they've achieved to stick.

"I think it's important the public know they should only be prescribed when needed, and by a medical professional who can oversee the treatment plan."

If you've read about Mounjaro on Mumsnet or seen it mentioned in the news, and you think it could be suitable for you, book an appointment to talk things through.

Your GP or specialist team can help you decide whether tirzepatide fits within your broader diabetes or weight management plan - and if not, they can guide you towards alternatives that might work better for your personal circumstances.

What happens when you stop taking Mounjaro?

The honest answer is that many people will regain some or all of the weight they lost. This isn't a failure - instead, a reflection of how the medication works on appetite-regulating hormones that return to their previous state once treatment stops.

What to expect after stopping

Weight regain is common because:

  • Appetite-regulating hormones (GLP-1 and GIP) return to baseline

  • "Food noise" and cravings typically return

  • Metabolic adaptations from weight loss make regain easier

Most people notice increased appetite within one to two weeks, with gradual weight regain over three to six months. Some plateau at a lower weight than their starting point, though not always.

To minimise weight gain, work with your healthcare team on gradual dose reduction rather than stopping abruptly. Work on sustainable habits like nutrition, movement, sleep and stress management - and also address any emotional eating coping strategies you can continue.

Is stopping Mounjaro safe?

Yes, there are no dangerous withdrawal symptoms. However you should discuss with your doctor rather than stopping suddenly.

Related: Everyday habits that improve your heart health

For additional information about diabetes management and treatment options:

Handling side effects

NHS resources

Professional organisations

Reporting concerns

Always consult your healthcare provider for personalised medical advice regarding your diabetes management and treatment options.

🔎 This article has been medically reviewed

Last reviewed in August 2025 by Dr David Porter MBBS, MSc, PgDip, an internationally renowned sports medicine physician and Founding Director of Opus.

Learn more

About the expert

  • Dr Daniel Atkinson is the Clinical Lead at Treated.com, an online healthcare service company.

About the author

Our resident Leeds lass, Rebecca Roberts is a Senior Content Editor here at Mumsnet. On a daily basis, she commissions, writes and edits content designed to help parents navigate real life - from product reviews to practical features on everything from sex and relationships to fashion to skincare.

Rebecca - aka Beccy - brings unique personal insight to weight loss content here at Mumsnet, having undergone her own journey with medically supervised injections. Her firsthand experience with GLP-1 treatments provides authentic expertise that resonates with parents exploring similar options. 

Beyond her role as an editor, she can be found balancing life as a working mum of two toddlers and when she’s not at her desk, you’ll likely find her at a PTA meeting, in a nearby coffee shop, or walking her two dogs up and down country lanes.

Read next: Weight loss injections - should you consider them?


*MumsGPT 1 January 2025 - 12 August 2025