The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Pros and Cons of Mounjaro in the UK
Mounjaro (tirzepatide) is a prescription weight loss injection licensed in the UK that has generated significant interest among people seeking support with weight management. Like all medications, it offers both benefits and limitations. Understanding the advantages and drawbacks helps you make an informed decision about whether it's right for you. This guide covers the key pros and cons, NHS availability, and how Mounjaro compares to other weight loss options available in the UK.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Key Benefits and Drawbacks of Mounjaro in the UK
Main advantages: Mounjaro uses a dual GIP and GLP-1 mechanism, which may deliver stronger appetite suppression than single-mechanism alternatives like Wegovy. Clinical trials showed an average weight loss of 15–21% of body weight, with some users achieving results at lower doses. It's a once-weekly injection, making it convenient compared to daily alternatives. Many people report reduced food cravings and feel fuller after smaller meals.
Key drawbacks: Nausea and gastrointestinal side effects are very common, especially when starting or increasing doses—some people experience vomiting or constipation that persists for weeks. Mounjaro is prescription-only and requires a clinical assessment, meaning you cannot simply decide to use it. Weight loss is not assured; individual results vary significantly. It's also expensive if accessed privately (typically £150–£280 per month depending on dose), and hair loss has been reported by some users.
- Requires ongoing prescription and monitoring
- Side effects can affect quality of life during dose titration
- Long-term safety data (beyond 2 years) is still emerging
- Requires lifestyle changes (diet and exercise) to maximise results
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
NHS Access vs Private Routes in the UK
NHS route: Mounjaro is approved by NICE for use within NHS specialist weight management (tier 3) services, but access is limited. You'll need a GP referral and a formal assessment by a specialist team—waiting lists can be many months or over a year in some areas. When available, the NHS covers the full cost, but availability depends heavily on your local Integrated Care Board (ICB).
Private route: Available through UK-licensed prescribers via online consultation, typically costing £150–£280 monthly for the standard doses. You skip NHS waiting lists but pay out of pocket. A clinical assessment still applies—prescribers will review your health history and eligibility (BMI ≥30, or ≥27 with weight-related health conditions).
Try our GLP-1 weight loss calculator to estimate projected results at different Mounjaro doses, and use the BMI calculator to check your current eligibility status.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How does Mounjaro compare to Wegovy for weight loss?
Mounjaro uses a dual GIP and GLP-1 mechanism versus Wegovy's single GLP-1 pathway. Clinical trials showed Mounjaro averaging 15–clinically studied weight loss versus Wegovy's ~15%, though individual results vary. Both are once-weekly injections, but Mounjaro may work faster for some people. Mounjaro KwikPen doses range up to 15mg weekly; Wegovy up to 2.4mg. A prescriber can help determine which suits your situation.
What are the most common side effects when starting Mounjaro?
Nausea is the most common, affecting more than 1 in 10 users. Diarrhoea, constipation, vomiting, and stomach pain also occur frequently, especially in the first 4 weeks. These typically improve over time as your body adjusts. Starting at a low dose (2.5mg) and increasing gradually helps minimise side effects. If side effects persist, discuss alternatives with your prescriber.
Can I get Mounjaro on the NHS in the UK?
Yes—NICE has approved tirzepatide for NHS specialist weight management services (tier 3). However, availability varies significantly by region, and waiting times can exceed 12 months. You'll need a GP referral and a formal assessment. Check with your local Integrated Care Board for current eligibility and waiting times. Private access is available faster but costs around £150–£280 monthly.
Is Mounjaro a permanent weight loss solution?
No. Mounjaro is a weight management tool, not a permanent supports. Weight loss results require continued use alongside a reduced-calorie diet and increased physical activity. Most people who stop taking Mounjaro experience weight regain within months. It works best as part of a long-term lifestyle approach rather than a one-off treatment.
What should I do if I'm interested in trying Mounjaro?
Start by booking an appointment with your GP to discuss weight management options. They can refer you to NHS specialist services if eligible, or you can pursue a private prescription through a UK-licensed online prescriber. Either way, a clinical assessment is required to confirm suitability based on your BMI, health history, and any weight-related conditions. Ensure you're ready to commit to lifestyle changes for best results.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.