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
Expected Weight Loss With Mounjaro in the UK
Clinical trials show that Mounjaro (tirzepatide) may help adults lose an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. This dual GIP and GLP-1 receptor agonist works alongside reduced-calorie diet and increased physical activity. Understanding realistic expectations, access routes, and costs can help you decide whether this prescription weight loss injection is right for you. Use our free GLP-1 weight loss calculator above to see potential weight loss projections at different Mounjaro doses.
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 Much Weight Can You Lose With Mounjaro?
In the SURMOUNT-1 clinical trial, participants using Mounjaro achieved these average weight loss results over 72 weeks:
- 5 mg dose: approximately clinically studied weight loss
- 10 mg dose: approximately clinically studied weight loss
- 15 mg dose: approximately clinically studied weight loss
For context, a person weighing 100 kg might lose 15–21 kg on average at the highest dose. However, these are clinical trial averages — your individual results depend on factors including starting weight, dose tolerance, adherence to diet and exercise changes, genetics, and metabolic rate. Weight loss typically occurs gradually over weeks and months, not immediately. The dose titration schedule (starting at 2.5 mg and increasing every 4 weeks) means full results take time. Always discuss realistic timescales with your prescriber.
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.
Cost and Access: NHS vs Private Routes
NHS access: Mounjaro is approved by NICE for specialist weight management services in England, but availability varies by region. Access requires referral to a tier 3 or tier 4 weight management service through your GP — waiting lists can be months or years in many areas. If approved, the NHS covers the full cost.
Private access: Available through GPhC-registered online prescribing services following a clinical assessment. Costs typically range from £150–£300+ per month depending on dose. You pay for the prescription and medication directly. Private access is faster — often available within days — but requires payment upfront. Whichever route you choose, a licensed prescriber must assess your suitability first.
- 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 a realistic weight loss expectation with Mounjaro?
Clinical trials show an average of 15–clinically studied weight loss over 72 weeks, but individual results vary. Someone weighing 100 kg might lose 15–21 kg, while another person may lose less. Results depend on your starting weight, the dose you reach, how well you stick to dietary changes, and your individual metabolism. Always discuss realistic goals with your prescriber.
How long does it take to see weight loss on Mounjaro?
Weight loss is typically gradual. Most people start seeing changes within 4–8 weeks, with more significant loss by 12–16 weeks. The dose titration schedule (increasing every 4 weeks) means you reach full effectiveness slowly. Full trial results were measured at 72 weeks, so patience is important.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £150–£300+ per month depending on your dose and the prescribing service. The 5 mg starting dose is usually cheaper; higher doses (10–15 mg) cost more. Prices vary between providers, so it's worth comparing. NHS provision is free but access can involve long waiting lists.
Can I access Mounjaro through the NHS in the UK?
Yes — NICE has approved tirzepatide (Mounjaro) for NHS specialist weight management services in England. Access requires a GP referral to tier 3 or tier 4 services. Availability varies significantly by region (ICB), and waiting lists are often very long. Your GP can advise on local availability and referral pathways.
What happens if I stop taking Mounjaro?
Weight regain is common if lifestyle changes are not maintained. Clinical trials suggest that without continued treatment and dietary/exercise support, people tend to regain weight. This is why Mounjaro is used alongside — not instead of — lasting behaviour changes. Discuss long-term plans with your prescriber before starting.
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.