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
Free tracker included with every download this week
Does Mounjaro Work For Weight Loss?
Yes, clinical evidence shows that Mounjaro (tirzepatide) can support weight loss in many UK adults. In the SURMOUNT-1 trial, participants using Mounjaro lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. Mounjaro works by activating two natural hormone pathways that help regulate appetite and reduce food cravings. It's a prescription-only weekly weight loss injection that's available in the UK through NHS specialist services or private prescribing following clinical assessment. Like all weight loss medications, Mounjaro works best alongside a reduced-calorie diet and increased physical activity.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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.
How Mounjaro Works For Weight Loss
Mounjaro is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways that your body uses to regulate appetite and fullness. This dual action is what distinguishes Mounjaro from other weekly weight loss injections like Wegovy, which targets GLP-1 alone. When you take Mounjaro as a KwikPen injection once each week, it helps:
- Reduce hunger signals sent to your brain
- Increase feelings of fullness after eating smaller portions
- Slow how quickly food leaves your stomach
- Support better blood sugar control
These effects combined may help you consume fewer calories naturally — without the constant battle against hunger that makes many diets fail. The medication is not insulin and does not work the same way as diabetes treatments, even though some people with type 2 diabetes use it.
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.
Clinical Evidence: Does It Actually Work?
The evidence is strong. In the SURMOUNT-1 clinical trial, adults taking Mounjaro alongside diet and exercise changes lost an average of 15–21% of their starting body weight — equivalent to roughly 10–20 kg for someone starting at 100 kg. At the highest dose (15 mg), average weight loss reached approximately 21% of body weight. However, results vary: some people lose less, some lose more, and a small minority don't respond well. Weight loss typically continues for the first 6–12 months, then stabilises if you maintain the same dose and lifestyle. You can check your personal BMI and explore potential weight loss projections using our free GLP-1 weight loss calculator above, and track progress over time with our progress tracker.
- 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.
What is the average weight loss with Mounjaro in the UK?
Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks at the highest dose, alongside diet and exercise. For example, someone starting at 100 kg might lose 15–21 kg on average. Individual results vary considerably — your GP or prescriber can discuss what to realistically expect for your situation.
How long does it take to see weight loss results with Mounjaro?
Weight loss typically begins within the first 4 weeks, though the first few weeks focus on dose adjustment to minimise side effects. Meaningful weight loss usually becomes noticeable around 8–12 weeks. Maximum results are generally seen after 6–12 months of consistent use at a stable dose.
Is Mounjaro better than Wegovy for weight loss?
Both work, but they use different mechanisms. Mounjaro uses dual GIP+GLP-1 action, while Wegovy uses GLP-1 alone. Clinical trials suggest Mounjaro may produce slightly higher average weight loss, but direct comparison data is limited. Your prescriber will assess which suits your health profile best.
Can I get Mounjaro on the NHS in the UK?
Yes, NICE has approved tirzepatide (Mounjaro) for NHS use in specialist weight management services (tier 3/4). Access varies significantly by region and waiting lists can be long. Your GP can refer you to your local specialist service, or you can access it privately through a UK-licensed prescriber.
Will I keep the weight off after stopping Mounjaro?
Weight regain is common after stopping GLP-1 medications if diet and exercise habits don't stay consistent. Some people maintain results by continuing the medication long-term; others manage weight through sustained lifestyle changes. Your prescriber will discuss the best long-term plan for you.
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.