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Mounjaro (tirzepatide) for weight loss

Mounjaro is a weekly injection that works on two appetite hormones at once. Paired with dietitian coaching and habit change, it is built so the weight you lose is more likely to stay off.

How Mounjaro works

Mounjaro is the brand name for tirzepatide. Most weight-loss injections copy one appetite hormone, but Mounjaro copies two. It is a dual GLP-1 and GIP receptor agonist, so it works on two hormone systems at once: slowing how quickly the stomach empties, turning down hunger signals to the brain, and helping with blood-sugar control.

The result is feeling full sooner, staying full for longer, and finding it easier to eat less without constant cravings.

How you take it

It is a once-weekly injection you give yourself, into the tummy, thigh or upper arm. You start low and build up slowly so side effects stay manageable, beginning at 2.5 mg and stepping up to a 5 mg, 10 mg or 15 mg maintenance dose.

Higher is not always better. The step up from 2.5 mg to 5 mg usually gives a bigger benefit than the move to 15 mg, so the right dose balances results against how you feel, and a clinician helps you find it.

Results to expect

In the SURMOUNT-1 trial, people lost an average of 16.0% of their body weight on the 5 mg dose, 21.4% on 10 mg and 22.5% on 15 mg over 72 weeks, compared with 2.4% on a placebo. Most people lose 2 to 4% in the first month, then settle into a steady, sustainable rate.

Medication works best alongside changes to how you eat and live. In a 12-month study of Second Nature members on tirzepatide, average weight loss reached 22.1%, ahead of the medication trials alone.

Side effects and safety

Most side effects are mild and gut-related, such as nausea, diarrhoea and reduced appetite, and tend to be worst in the early weeks as the dose increases. In trials, more than 90% of people were able to stay on Mounjaro, and fewer than one in ten stopped because of side effects.

Rarer but more serious risks include pancreatitis and gallbladder problems. It is not suitable for everyone, including people with a personal or family history of medullary thyroid cancer, so a clinician always checks it is right for you before you start.

Who it is for

Mounjaro is a prescription-only medicine, so a clinician checks it is safe and suitable before you start. It is licensed for adults with a BMI of 30 or above, or 27 to 30 with a weight-related condition such as type 2 diabetes or high blood pressure.

It tends to suit people who have found it hard to lose weight through diet and lifestyle alone and do not have a condition that rules it out.

Everyone goes through a clinical eligibility check first.

What you get with Second Nature

The injection brings your appetite down, and what you do with that window decides whether the weight stays off.

Your plan pairs the prescription with a registered dietitian, daily coaching in the app, and a structured approach to food, movement and sleep, all built to help you lose weight and keep it off.

Frequently asked questions

How is Mounjaro different from other weight-loss injections?

Mounjaro is tirzepatide, a once-weekly injection. Most weight-loss injections copy one appetite hormone, but Mounjaro copies two, GLP-1 and GIP, which is why it tends to deliver more weight loss at standard doses.

How much weight can I lose on Mounjaro?

In the SURMOUNT-1 trial, people lost an average of 16.0% on 5 mg, 21.4% on 10 mg and 22.5% on 15 mg over 72 weeks. Second Nature members combining it with our programme lost an average of 22.1% over 12 months.

What doses does Mounjaro come in?

You start at 2.5 mg and build up gradually to a 5 mg, 10 mg or 15 mg maintenance dose, staying at each step long enough for your body to adjust.

What are the side effects of Mounjaro?

Most are mild and gut-related, such as nausea, diarrhoea and reduced appetite, and ease as the body adjusts. More than 90% of people are able to stay on it, and a clinician checks your suitability before you start.

Who should not take Mounjaro?

It is not recommended for anyone with a personal or family history of medullary thyroid cancer, and is used with caution in people with a history of pancreatitis or gallbladder problems. A clinician reviews your history before prescribing.

How often do I inject Mounjaro?

Once a week, on any day, into the tummy, thigh or upper arm.

Should I choose Mounjaro or Wegovy?

In a head-to-head trial, Mounjaro 15 mg produced 20.2% weight loss versus 13.7% for Wegovy 2.4 mg over 72 weeks. Mounjaro tends to suit people wanting the strongest results at standard doses, and a clinician helps you weigh it up.

Sources

Mounjaro weight loss (16.0% on 5 mg, 21.4% on 10 mg, 22.5% on 15 mg over 72 weeks): SURMOUNT-1 trial of tirzepatide.

Mounjaro versus Wegovy (20.2% vs 13.7% over 72 weeks): SURMOUNT-5 head-to-head trial.

Second Nature member outcomes (22.1% average at 12 months): internal study of members on tirzepatide.

What you'll get

Here’s everything that’s included in the cost of your monthly plan
Second Nature health kit box
New starter health kitWorth £120

Enjoy 100+ nutritious recipes and bluetooth scales with your first order.

Bluetooth scales
Recipe cookbook
Mounjaro penMonthly
Second Nature App
MORE THAN MEDICATION

The Complete Programme

All accessible via the app

12-month guided programme

Think of it like a masters for your health. A structured programme proven to build lasting habits and sustainable weight loss.

Worth £600

A dedicated nutritionist

Get a consultation and ongoing support from a dedicated nutritionist who will monitor your side effects and give you tailored health advice.

Worth £1,400

Monthly clinical reviews

Get ongoing clinical reviews, dose optimisation and a tailored plan to maintain and come off the medication when you're ready.

Worth £500

Exclusive member community

Join a close knit support group that shares your worries, wins and journey. You don't need to feel alone anymore.

Worth £150

Second Nature App (4.8★)

Our top rated app, used by the NHS allows you learn, track habits, plan meals and monitor your progress. You'll have free access for life.

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Health team in your pocket

The medication alone is not enough, we offer comprehensive human support so you're never left feeling stuck or alone.

Clinical oversight

Clinical oversight

Your clinician reviews your progress and plan each month.

1-1 health coaching

1-1 health coaching

Get personalised guidance on side effects and nutrition.

Customer support

Customer support

Our team is here to help with any technical issues or concerns.

Peer community

Peer community

Connect with others on a similar journey to you.

Weight loss is complicated

You don't need to figure it out alone anymore

Our team of doctors, psychologists, and dietitians guide your journey
Dr Rachel Hall
Dr Rachel Hall Doctor (MBCHB Oxon)
Dr Becky Richards
Dr Becky Richards Psychologist
Minty
Minty Dietitian (MDiet)
Second Nature App

The Second Nature App

Designed by psychologists.
Recommended by GPs. Used by the NHS.

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out of 5
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Break old habits and thought patterns to build lasting healthy habits

Handy tools and resources to support a healthy lifestyle and mindset

Improve your relationship with food. No deprivation or obsessive thoughts

Celebrate your progress. Track habits, weight, steps and sleep improvements

Member Stories

Join thousands of our members
transforming their health

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Anneka W. before

Day 1

Anneka W. after

Month 9

Anneka lost 38 kg

"I feel like I'm back to my old self, and I'm showing my kids and grandkids a different example."

Anneka W.

Steven W. before

Day 1

Steven W. after

Month 12

Steven lost 32 kg

"Nothing else worked for me until Second Nature. My clothes have gone from 5XL to Large."

Steven W.

Ann W. before

Day 1

Ann W. after

Month 9

Ann lost 19 kg

"After years of struggling to lose weight and always feeling uncomfortable in my body. I have finally found something that works for me."

Ann W.

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FAQs

What is weight loss medication?
Weight-loss medications like Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription treatments that help regulate appetite and support long-term weight loss.

They work by targeting the same hormones your body uses to manage hunger, fullness, and blood sugar, making it easier to eat less, feel satisfied sooner, and build healthier habits.
What is the difference between Wegovy, Mounjaro, and Orlistat?
Wegovy (semaglutide) and Mounjaro (tirzepatide) are both once-weekly injections that help most people to lose weight. However, they have different active ingredients. In Wegovy, the active ingredient is semaglutide and in Mounjaro the active ingredient is tirzepatide. Orlistat, unlike Wegovy and Mounjaro, comes in the form of a pill that is taken up to three times a day, every day. Wegovy is used solely for weight loss and works by mimicking a single hormonal receptor (GLP-1) which slows down gastric emptying, making you feel fuller for longer. Mounjaro activates both the GLP-1 receptor as well as the GIP receptor, which promotes energy storage. Mounjaro is used for both weight loss and for managing type 2 diabetes. Both GIP and GLP-1 receptors are expressed in the areas of the brain important for appetite regulation. Orlistat works in the stomach and intestines by blocking the enzymes (lipases) that break down dietary fats. This in turns prevents a percentage of the fats you've eaten (approximately one-third) from being absorbed into the body. Instead, this undigested fat is excreted with your stools. This ultimately creates a calorie deficit that aids in weight loss. Because Wegovy and Mounjaro are different medications, this also means that their starting, escalation doses and maintenance are different. They also have different manufacturers: Wegovy is made by Novo Nordisk, whilst Mounjaro is made by Eli Lilly. Orlistat is available in the UK in two different dose strengths depending on patient eligibility: a 60mg Pharmacy Medication and a 120mg Prescription Only Medication. However, there is no escalation process; patients start and maintain on the same dose for the duration of their treatment. This service only offers the 60mg dose of Orlistat, which is made by Haleon UK Trading Limited.

If you want a deeper breakdown, read our Wegovy vs Mounjaro comparison guide.
Is it safe?
Yes, when prescribed responsibly and monitored by a qualified clinician.

GLP-1 medications are well-studied, with strong safety records from long-term clinical trials.

However, like all medications, they aren't suitable for everyone. That's why we complete a detailed health assessment before prescribing.
Is the medication safe with my existing conditions (HRT, thyroid issues, previous gallbladder removal)?
We can't give you a yes or no without completing our health assessment; the clinical prescribing clinician will evaluate your individual situation.

Previous gallbladder removal, certain thyroid conditions, and other health issues require careful consideration but in many circumstances, you can take Mounjaro alongside these conditions. HRT typically isn't a problem.

The onboarding includes a detailed health questionnaire and clinical review. Be completely honest about your health history.
What happens when I stop taking the medication? Will I regain weight?
It depends on the habits you've built while on medication. Research shows people typically regain two-thirds of lost weight without proper support.

Our data suggests something different: participants who develop sustainable habits with our programme show only 3.2% weight regain after stopping, compared to 6%+ without support.

We focus on building these habits from day one; when appetite is lower and it's easier to learn what healthy eating actually looks and feels like.

The medication gives you a window to change your relationship with food, not just lose weight temporarily.
What support do I get from my health coach? How do I communicate with them?
Your health coach is a UK-registered dietitian or nutritionist, available 5 days a week through the app. You message them directly and get responses typically same day.

They help with managing side effects, adjusting eating habits as your appetite changes, and building practical skills around food. You're also placed in a small group with others on similar journeys for peer support.

The support continues throughout your programme, not just at the start.
Can I stay on a lower dose if it's working for me?
Yes, you can stay on a dose that's working well for you.

Some people find excellent results at 5 mg or 7.5 mg of Mounjaro and choose to stay there.

Others need to gradually move up to 15 mg. The clinical team will work with you to find what's right based on your weight loss, side effects, and goals.

It's not one-size-fits-all; the decision is made together with the clinical team.
Can I switch to Second Nature from another provider and keep my current dose?
Yes, in most cases you can continue your current dose after a clinical assessment.

Our prescribing pharmacists will review your current medication, how long you've been taking it, and your medical history. If you're stable and everything checks out medically, you can typically continue rather than starting from the beginning.

You'll complete a health questionnaire and have a consultation with our clinical team, then get access to the full programme alongside your medication.
Can I cancel or pause at any time? Am I locked into a contract?
You can cancel anytime with no penalties or a long-term contract.

If you're thinking about cancelling because of side effects, cost, or feeling stuck, it's worth speaking to your health coach first - they might be able to help.
How do I get help if I experience severe side effects?
For mild side effects like nausea or constipation, message your health coach.

For moderate or persistent issues, they'll escalate to the clinical team. For severe symptoms (severe abdominal pain, allergic reactions), contact 111 or go to A&E immediately; don't wait to message us first.

Common side effects typically improve over time. Our research showed 69% of participants reported no side effects by month 12.
Who is your clinical team? Are they qualified doctors?
Our prescribing team are independent prescribing pharmacists registered with the General Pharmaceutical Council. They handle all medication decisions and clinical oversight.

Your health coaches are UK-registered dietitians or nutritionists with specialist training in GLP-1 medications. Dr Rachel Hall (MBChB) provides medical review and oversight.
How is Second Nature different from other providers?
We've had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.

Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro and Wegovy) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.

At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We're here to support that change every step of the way.

With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK's most trusted weight-loss programme.

We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.

If you're comparing providers, you can also read our guides on how to buy Mounjaro online and buy Wegovy online.
Can I switch between weight loss medications?
Yes. If you find that one medication isn't working for you, either because you aren't losing enough weight or because the side effects aren't tolerable, let the clinician know. The clinician will typically have a discussion with you to determine what the issue is and if a change in medication would be in your best interest. You should note that some of the weight loss medications work similarly and have similar side effects. Therefore, switching medications does not necessarily mean that you'll lose more weight or that your side effects will change. When you switch from one medication to another, the same protocol is followed as if you are starting your weight loss journey afresh. This means that you will be prescribed the lowest dose of the new medication to begin and then gradually you'll work up to larger doses as your tolerability increases.
Can I start at a higher dose?
For Wegovy (semaglutide) and Mounjaro (tirzepatide), not unless you're already being prescribed the same weight loss medication by another provider. For Orlistat, there is only one dose offered on this service, and there is no escalation/titration path. Both Wegovy and Mounjaro have been designed with a set titration path for your safety and wellbeing (a titration path is when the dose is increased each month). This staggered approach also helps to reduce the impact of any gastrointestinal (GI) side effects by giving your body time to adjust to the medication. Some patients may even find that they need to titrate more slowly than other patients in order to give their body more time to get used to the medication.
Why are there different dose strengths?
For Orlistat, whilst there are two dose strengths available in the UK, only one dose strength (60mg) is available on this service. The difference in dose strengths for Orlistat is tied to patient eligibility and how much oversight from a clinician is required. The different doses of Wegovy and Mounjaro are part of a set titration path with your safety and wellbeing in mind. Weight loss medications commonly cause gastrointestinal (GI) side effects. The titration path for both Wegovy and Mounjaro starts you at a low initial dose of medication and then gradually increases your dose over time. This helps to reduce the impact of these side effects by giving your body time to adjust.
Do I have to increase my dose each month?
That depends. While most patients follow the set titration path for Wegovy and Mounjaro (which means that their dose is increased each month), other patients remain on the same dose for more than 1 month in order to allow their body more time to adjust to the medication. It all comes down to your body and how you tolerate the medication. The clinician will work with you to ensure that the next dose up is safe and effective for you. If you're having more side effects than usual, or you find that the side effects aren't tolerable, let your clinician know. You may be prescribed the same dose again or, in some cases, have your dose lowered if needed. If you're taking Orlistat, your dose won't increase at all. You'll take the same dose of the medication throughout your treatment.
How quickly will I lose weight?
Many patients start to notice weight loss within a month of starting medication. However, for some patients, it can take longer. Based on a clinical trial, patients taking 2.4 mg of Wegovy (semaglutide) can expect to lose up to 15% of their body weight after 68 weeks. In a separate clinical trial, patients taking Mounjaro (tirzepatide) 10 mg or 15 mg lost up to 20% of their body weight after 36 weeks. For patients taking Orlistat 60mg in a clinical trial, 46% lost at least 5% of their body weight in 6 months and 16% of patients lost 10%. In all clinical trials, patients were using the medication alongside a change in lifestyle (i.e. a reduced calorie diet and increased physical activity). If within six months of being on Wegovy or Mounjaro, or within three months of being on Orlistat, you do not lose at least 5% of your body weight, the clinician will work with you to understand why and, together, you'll decide if it is in your best interest to continue with the medication.
How long will I need to take the medication?
For Wegovy and Mounjaro, this is entirely up to you. The medications prescribed are intended for long-term use and sustainable weight maintenance, rather than being a quick fix. Once your rate of weight loss has stabilised and/or you've reached your target weight, the clinician will have a chat with you to understand whether continuing your weight loss treatment is in your best interest. For Orlistat, treatment should not exceed six months.
What if I don't lose any weight?
Some patients start to lose weight within a month of starting medication, but for others it may take longer. It's important to consistently take your medication as prescribed and to make diet and lifestyle changes alongside this. If within six months of being on Wegovy or Mounjaro, or within three months of being on Orlistat, you do not lose at least 5% of your body weight, the clinician will work with you to understand why and, together, you'll decide if it is in your best interest to continue with the medication.
What if I need to take a break from my weight loss medication?
This is entirely understandable. However, you should note that the medication is designed to be used long-term, without gaps or breaks. It takes time for your body to get used to the medication and, for Wegovy and Mounjaro, for you to build up your tolerance of the maintenance dose. Because of this, a gap or break of 2 doses or more when taking Wegovy or Mounjaro typically means that you'll need to start over. This means you'll have to begin on the starting dose when you decide to start taking the medication again. Orlistat is designed for consistent, daily use alongside meals containing fat, but it can be taken intermittently if you miss a meal or eat a fat-free meal. If you regularly need to take breaks from medication, it may be worth discussing this with the clinician to determine whether the medications prescribed are the most appropriate course of action for you.
Will I get side effects?
Weight loss medications commonly cause gastrointestinal (GI) side effects. These should subside in time and, in many instances, can often be managed by diet modification and over the counter medications. Side effects are most likely to be experienced during dose escalations (if you are taking Wegovy or Mounjaro) or when you first start treatment (if you are taking Orlistat). Some of the very common side effects for Wegovy (affecting 1 in 10 patients) include: Headaches, Vomiting, Diarrhoea, Constipation, Nausea, Bloating, Fatigue, Weakness. Some of the very common side effects for Mounjaro (affecting 1 in 10 patients) include: Vomiting, Diarrhoea, Constipation, Nausea. Some of the very common side effects for Orlistat (affecting 1 in 10 patients) include: Oily spotting, Flatus (gas) with discharge, Faecal urgency, Fatty oily stool, Oily evacuation, Flatulence (gas), Soft stools.

You can also read our detailed Mounjaro side effects guide and Wegovy side effects guide.
What can I do to manage common side effects effectively?
For nausea and mild abdominal pain, try reducing your meal size. Aim for smaller, more frequent meals that have an appropriate protein content and are not high in fat. Eat slowly, remain hydrated, and focus on simple, plain foods. If your lack of appetite is extreme, it's important to set reminders to eat and maintain proper nutrition. It may help to keep a food diary, or to eat whenever you do feel hungry, even if this is not at a normal mealtime. For issues with bloating, try to remember to eat small, more frequent meals and to eat slowly. Avoid fizzy drinks and be sure to take small sips. If you are experiencing headaches, stay hydrated and avoid too much screen time. It may also be helpful to get some fresh air and to lie down for a rest or take a nap. When diarrhoea occurs, it's important to stay hydrated and avoid caffeine. Continue to eat, but make sure your meals are small and frequent and that you eat slowly. Reduce your intake of fatty foods and insoluble fibre and consider taking some probiotics. If instead you become constipated, ensure that you remain hydrated and move about regularly. Consume regular and balanced meals and check your overall intake of fibre. If you are experiencing side effects associated with Orlistat, try reducing your dietary consumption of fat.
Are the medications addictive?
No, Wegovy, Mounjaro, and Orlistat are not addictive or habit-forming.