Mounjaro for Weight Loss: Benefits, Risks and Everything You Need to Know

Medically reviewed by Imtiaz B., Superintendant – Longridge Travel Health Clinic

Mounjaro (tirzepatide) has quickly become one of the most effective prescription weight loss treatments available in the UK. Originally developed for type 2 diabetes, it was approved by the MHRA for weight management in late 2023 and is now prescribed by private clinics and, since March 2025, through NHS specialist weight management services for eligible patients.

The results are striking. In the landmark SURMOUNT-1 clinical trial, patients taking Mounjaro lost up to 22.5% of their body weight over 72 weeks on the highest dose – making it around six times more effective than diet and exercise alone. But as with any medication, understanding the benefits and risks before you start is essential.

In this guide, we’ll cover how Mounjaro works, its proven benefits beyond just weight loss, the potential side effects and risks, who’s eligible, and how it compares to alternatives like Wegovy. Whether you’re weighing up your options or ready to start, this article will give you the complete picture.

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What is Mounjaro?

Mounjaro is a prescription injectable medication containing the active ingredient tirzepatide. It was developed by Eli Lilly and originally approved for managing type 2 diabetes. Following successful clinical trials demonstrating significant weight loss, it received UK approval for weight management in adults living with obesity or overweight with weight-related health conditions.

It’s taken as a once-weekly injection using a pre-filled pen. You inject it under the skin of your abdomen, thigh, or upper arm, on the same day each week. The dose starts low at 2.5mg and can be gradually increased up to a maximum of 15mg, based on how your body responds and your clinician’s guidance.

Mounjaro is classified as a dual GIP/GLP-1 receptor agonist – a type of medication that mimics two natural hormones involved in appetite regulation and metabolism. This dual-action approach is what makes it particularly effective, and it’s what sets it apart from single-action GLP-1 treatments like Wegovy (semaglutide).

How Does Mounjaro Work for Weight Loss?

Understanding how Mounjaro works helps explain why it’s so effective. It targets two key hormone pathways that control appetite, digestion, and blood sugar.

• GLP-1 (glucagon-like peptide-1): This hormone signals to your brain that you’re full, reduces appetite between meals, and slows the speed at which food leaves your stomach (known as gastric emptying). When food stays in your stomach longer, you feel satisfied for longer after eating, making it much easier to eat less without feeling deprived.
• GIP (glucose-dependent insulinotropic polypeptide): This second hormone works alongside GLP-1 to improve how your body manages insulin and processes energy. It enhances the appetite-suppressing effects of GLP-1 and helps your body regulate blood sugar more effectively, reducing the energy crashes and cravings that often lead to overeating.

By activating both of these pathways simultaneously, Mounjaro creates a powerful combined effect on weight regulation. You feel less hungry between meals, you feel full faster when you do eat, food stays in your stomach longer, and your blood sugar remains more stable throughout the day. This makes it significantly easier to maintain a consistent calorie deficit – the foundation of sustainable weight loss.

This dual-action mechanism is also what makes Mounjaro more effective than single-action GLP-1 medications. In the SURMOUNT-5 head-to-head trial, tirzepatide produced greater average weight loss than semaglutide (Wegovy) over 72 weeks. If you’re interested in how Mounjaro compares to Wegovy in more detail, read our guide on safely switching from Mounjaro to Wegovy.

Benefits of Mounjaro

Mounjaro’s benefits extend well beyond the number on the scales. Here’s what the clinical evidence and our own experience with patients at Longridge Travel Health Clinic shows.

Significant, Clinically Proven Weight Loss

The primary benefit of Mounjaro is its ability to support substantial, sustained weight loss. In the SURMOUNT-1 trial, participants lost an average of 16% (5mg), 21.4% (10mg), and 22.5% (15mg) of their starting body weight over 72 weeks. Over 90% of patients on the higher doses lost at least 5% of their body weight, which is the threshold considered clinically meaningful for improving metabolic health.

For a practical understanding of how this weight loss unfolds over time, see our Mounjaro results week by week guide.

Improved Blood Sugar Control
Mounjaro was originally developed for type 2 diabetes, and it remains highly effective at lowering blood sugar levels. It increases insulin secretion when blood sugar is elevated (reducing the risk of hypoglycaemia), improves insulin sensitivity, and reduces the amount of glucose released by the liver. For patients with prediabetes, the three-year SURMOUNT-1 data showed that tirzepatide reduced the risk of developing type 2 diabetes by 94%.

Cardiovascular and Metabolic Improvements
The weight loss associated with Mounjaro doesn’t just change your appearance – it improves measurable health markers. Clinical trial participants experienced reductions in blood pressure, triglycerides, and waist circumference. Research also suggests potential benefits for heart failure with preserved ejection fraction, with one trial showing a 38% reduction in major cardiovascular complications compared to placebo.

Reduced Appetite and Fewer Cravings

One of the most consistently reported benefits by our patients is a fundamental shift in their relationship with food. Many describe feeling genuinely satisfied with smaller meals, experiencing far fewer cravings, and no longer thinking about food constantly. This isn’t willpower, it’s the medication working on the hormonal signals that drive hunger.

Convenient Once-Weekly Injections

Unlike daily medications, Mounjaro is taken just once a week using a simple pre-filled pen. The injection takes only a few seconds and most people find it easy to self-administer after the first time. This makes it far easier to maintain consistency compared to treatments that require daily dosing.

Benefits Beyond Weight Loss

Emerging research and patient reports point to additional benefits of Mounjaro that go beyond weight and blood sugar, including improved sleep quality (particularly for those with obstructive sleep apnoea), increased energy levels and physical mobility, reduced joint pain as excess weight decreases, and improvements in mood and confidence. While these aren’t the primary indications for the medication, they represent meaningful quality-of-life improvements that many patients experience during treatment.

Is Mounjaro Safe?

This is one of the most important questions people ask before starting treatment, and rightfully so. The short answer is: yes, Mounjaro is considered safe when prescribed appropriately and monitored by a qualified healthcare professional.

Mounjaro has been evaluated in extensive clinical trials involving thousands of participants worldwide. It is approved by the MHRA (UK), the EMA (Europe), and the FDA (US) for both diabetes management and weight loss. These regulatory bodies conducted rigorous reviews of its safety profile before granting approval.

That said, like all medications, Mounjaro does carry potential side effects and risks that you should understand before starting treatment.

Common Mounjaro Side Effects

The most frequently reported side effects are gastrointestinal and are typically mild to moderate. They tend to occur most during the early weeks of treatment and when the dose is increased, then ease as your body adjusts.

These include nausea (the most common, affecting around 24–31% of trial participants), diarrhoea, constipation, abdominal discomfort or bloating, reduced appetite, and mild injection site reactions such as redness or itching. At Longridge Travel Health Clinic, we provide practical guidance on managing these side effects from the outset, and the vast majority of our patients find they settle within the first few weeks of treatment.

Less Common but Serious Risks

Pancreatitis: Inflammation of the pancreas occurs in fewer than 1% of patients. It typically presents as severe abdominal pain that may radiate to the back, sometimes with vomiting. The risk is slightly higher in people with a previous history of pancreatitis. Seek immediate medical attention if you experience severe, persistent abdominal pain.

Gallbladder problems: Approximately 2.5% of patients in clinical trials developed gallbladder issues, including gallstones. This is often related to the rapid weight loss itself rather than the medication directly. Staying hydrated and eating regular, balanced meals can help reduce this risk.

Allergic reactions: Serious allergic reactions are rare (affecting fewer than 0.1% of users) but can include swelling of the face, lips, tongue, or throat, difficulty breathing, or a rapid heartbeat. If you experience any of these symptoms, stop taking Mounjaro and seek emergency medical care immediately.

Thyroid concerns: In animal studies, tirzepatide caused thyroid C-cell tumours in rats. It is not yet known whether the same risk applies to humans. As a precaution, Mounjaro should not be used by people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

How to Monitor Your Mounjaro Treatment Safely

The best way to manage the risks above is not to avoid them – it is to monitor for them. The serious side effects associated with Mounjaro, particularly pancreatitis, liver strain and kidney effects, almost always show up in a blood test before they become a serious clinical problem. A simple blood panel before you start treatment, and again at sensible intervals during treatment, gives you and your clinician objective data to work from.

Three markers are especially worth watching on Mounjaro:

• Lipase and Amylase – the two pancreatic enzymes that become elevated early in pancreatic inflammation, often before you’d notice symptoms.
• ALT, AST and GGT – liver enzymes that reveal whether your liver is under strain. Helpful because fatty liver is common in people carrying excess weight, and rapid weight change can itself affect these markers.
• Creatinine and eGFR – kidney markers that matter because GLP-1 side effects like vomiting or reduced fluid intake can affect kidney function.

At Longridge Travel Health Clinic, we offer three tiered weight loss blood tests designed specifically for patients on GLP-1 medications:

• The Essential test (£99) covers all the core safety markers and is suitable for most patients at baseline. If you have a personal or family history of thyroid disease, or you’re struggling to lose weight despite treatment
• The + Thyroid test (£115) adds TSH and Free T4. For patients on higher doses or a long maintenance course
• Our Advanced test (£179) adds a full blood count, iron status, and Vitamin D and B12 – catching the nutritional deficiencies that often show up as “unexplained” fatigue after months on treatment.

A sensible monitoring rhythm for most patients is: a baseline test before your first injection, a follow-up at weeks 4–8 when your dose first increases, a fuller check at 3 months, and then every 3–6 months on maintenance. Your clinician will adjust this based on your individual response.

Why Proper Screening Matters

This is exactly why a thorough medical assessment before starting Mounjaro is essential. At Longridge Travel Health Clinic, our Patient Access Evaluation reviews your full medical history, current medications, and any existing health conditions to identify potential contraindications. If Mounjaro isn’t right for you, we’ll discuss suitable alternatives – including Wegovy and other approaches to losing weight sustainably.

Mounjaro Pros and Cons at a Glance

Pros	Cons
Clinically proven weight loss up to 22.5%	Gastrointestinal side effects, especially early on
Dual-action mechanism (more effective than single-action GLP-1s)	Not currently widely available on the NHS for weight loss
Improves blood sugar, blood pressure, and cholesterol	Private prescriptions can be costly
Convenient once-weekly injection	Requires ongoing treatment for sustained results
May reduce risk of developing type 2 diabetes	Weight regain possible if stopped without lifestyle changes
Supported by extensive clinical trial data (SURMOUNT programme)	Small risk of serious side effects (pancreatitis, gallbladder)

Can Mounjaro Deliver Long-Term Weight Loss?

One of the key concerns with any weight loss treatment is whether the results last. The evidence for Mounjaro is encouraging, but it comes with an important caveat.

The three-year follow-up data from SURMOUNT-1 showed that weight loss was sustained throughout the full treatment period in patients who continued taking the medication. However, when treatment was stopped after 72 weeks, participants experienced weight regain during the 17-week off-treatment period.

This is why we emphasise to every patient that Mounjaro is most effective as part of a comprehensive approach to weight management – not as a standalone solution. The medication gives you a powerful advantage, but building sustainable habits around nutrition, movement, and lifestyle is what locks in the results for good. For practical advice on this, see our guide to the best way to lose weight and keep it off for good.

At Longridge Travel Health Clinic, every patient receives personalised guidance on nutrition, physical activity, and healthy habits alongside their Mounjaro prescription. This combined approach gives you the best chance of maintaining your results long after treatment ends.

Mounjaro vs Wegovy: How Do They Compare?

Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are effective injectable weight loss medications, but they work slightly differently.

Feature	Mounjaro (Tirzepatide)	Wegovy (Semaglutide)
Mechanism	Dual GIP + GLP-1	GLP-1 only
Avg. Weight Loss (72 weeks)	Up to 22.5%	~15–17%
Frequency	Once weekly	Once weekly
Starting Dose	2.5mg	0.25mg
Max Dose	15mg	2.4mg
UK Availability	Private + NHS (limited)	Private + NHS (limited)
Common Side Effects	Nausea, diarrhoea, constipation	Nausea, diarrhoea, constipation

In head-to-head trials, Mounjaro consistently produced greater average weight loss than Wegovy. However, both are effective treatments and the best choice depends on your individual health profile, tolerance, and goals. We offer both treatments at Longridge Travel Health Clinic and can help you decide which is most appropriate. If you’re currently on one and considering switching, read our guide on how to safely switch from Mounjaro to Wegovy.

Is Mounjaro Right For You? Eligibility Criteria

Mounjaro may be a suitable option for you if you meet certain criteria. In the UK, eligibility for Mounjaro for weight management typically requires that you are an adult with a BMI of 30 or above (classified as obese), or an adult with a BMI of 27 or above with at least one weight-related health condition such as type 2 diabetes, high blood pressure, high cholesterol, obstructive sleep apnoea, or cardiovascular disease.

You should also have tried to lose weight through diet and exercise changes without achieving sustainable results, and you should be willing and able to make ongoing lifestyle changes alongside the medication.

Who Should Not Take Mounjaro?

Mounjaro is not suitable for everyone. It should not be used by people with a personal or family history of medullary thyroid carcinoma or MEN 2, people with a history of severe pancreatitis, those who are pregnant, planning to become pregnant, or breastfeeding, or anyone with a known hypersensitivity to tirzepatide or any of the injection’s ingredients. If you have type 1 diabetes, severe gastroparesis, or certain other medical conditions, your clinician will assess whether Mounjaro is appropriate for you on an individual basis.

At Longridge Travel Health Clinic, our Patient Access Evaluation is designed to thoroughly assess your eligibility. We review your medical history, current medications, and health conditions to ensure Mounjaro is safe and appropriate for you before prescribing.

Cost and Access: Getting Mounjaro in the UK

As of March 2025, Mounjaro (tirzepatide) became available on the NHS for eligible patients through specialist weight management services, but initial access is limited to those with the highest clinical need. The NHS rollout is being phased, meaning not everyone who meets the criteria will be able to access it immediately through their GP.

For patients who want quicker access, private prescriptions offer an alternative. At Longridge Travel Health Clinic, we offer Mounjaro privately with personalised clinical support. Private care offers several advantages: faster access to treatment, one-to-one clinical consultations, flexible appointment scheduling, ongoing monitoring and dose adjustments, and direct access to your prescribing clinician for questions or concerns.

We understand that cost is a consideration, and we’re transparent about our pricing. Visit our Mounjaro service page for current prices, or contact us to discuss your options.

If you’re based in the local area, you may also be interested in our dedicated page on Mounjaro for weight loss in Lancashire, which covers local availability and how our Longridge clinic serves patients across Preston, Blackburn, and the wider Lancashire area.

Frequently Asked Questions About Mounjaro

Take the First Step

Mounjaro represents a significant advancement in weight management, offering clinically proven, substantial weight loss alongside meaningful improvements in metabolic health. For most people, it is safe and well tolerated when prescribed and monitored correctly.

The most successful outcomes come when Mounjaro is used not as a quick fix, but as one part of a broader, personalised approach to improving your health. That means combining the medication with better nutrition, regular movement, and ongoing clinical support.