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
Will I Lose Weight On Mounjaro?
Yes, clinical evidence suggests Mounjaro can help with weight loss in many people, though individual results vary significantly. In the SURMOUNT-1 trial, adults taking Mounjaro lost an average of 15–21% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity. However, weight loss is not assured—your results will depend on your starting weight, how well you follow the prescribed dose titration schedule, lifestyle changes, and individual factors. This guide explains what the evidence shows, how much Mounjaro costs in the UK, and how to access it through NHS or private routes.
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.
Mounjaro Weight Loss Evidence & Cost in the UK
Clinical trials show Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist weekly weight loss injection, can support meaningful weight loss when combined with lifestyle changes. In the SURMOUNT-1 trial, participants on the maximum 15 mg dose lost an average of 20.9% of their body weight—equivalent to roughly 15–25 kg for many adults, though results vary considerably.
Average weight loss by dose:
- 5 mg dose: approximately clinically studied weight loss
- 10 mg dose: approximately clinically studied weight loss
- 15 mg dose (maximum): approximately clinically studied weight loss
These figures represent trial averages and assume consistent adherence to the prescription weight loss injection schedule, a reduced-calorie diet, and regular physical activity. Your personal outcomes may differ. Mounjaro works by activating appetite-regulating hormones and supporting satiety, helping you feel fuller after smaller meals. Weight loss typically continues through the dose titration phase (weeks 1–20) and maintenance phase.
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 vs Private Access: How to Get Mounjaro in the UK
NHS route: Mounjaro is available through specialist tier 3 weight management services, but access is highly variable by region. You'll need a referral from your GP, and waiting lists can extend months or longer in many areas. Once referred, a specialist team assesses your eligibility based on BMI and health conditions before prescribing.
Private route: You can access Mounjaro through private online consultations with UK-licensed prescribers without NHS referral. After an online health assessment, a prescription is issued if clinically appropriate and dispensed by a GPhC-registered pharmacy. Private costs typically range from £129–£320 per month depending on your dose. Private access is faster—often within days—but requires payment upfront.
Whichever route you choose, use our free BMI calculator and GLP-1 weight loss calculator to understand your starting point and project realistic outcomes based on clinical evidence.
- 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.
Will Mounjaro definitely help me lose weight?
No. While clinical trials show Mounjaro helps most people lose weight, individual results vary. Success depends on adherence to your dose schedule, following a reduced-calorie diet, increasing physical activity, and your personal metabolism. Your GP or prescriber can discuss realistic expectations for your situation.
How much does Mounjaro cost on the NHS?
Mounjaro is free on the NHS if prescribed through a specialist weight management service. However, access depends on your region and meeting eligibility criteria. Your GP can refer you to your local tier 3 service to check availability and waiting times.
What's the typical cost of private Mounjaro in the UK?
Private costs typically range from £129–£320 per month depending on your dose. Starting doses (2.5–5 mg) are usually cheaper; higher doses (10–15 mg) cost more. Prices vary between providers, so compare options before committing.
How quickly will I see weight loss on Mounjaro?
Most people notice changes within the first few weeks, though significant weight loss typically develops over 8–12 weeks as your dose increases through the titration phase. The dose titration schedule starts at 2.5 mg weekly and increases every 4 weeks to reach your target dose.
Is Mounjaro the same as a weekly weight loss injection?
Yes. Mounjaro is a once-weekly injectable medication. Other weekly weight loss injections available in the UK include Wegovy (semaglutide). Your prescriber will recommend the option most suitable for your health profile and needs.
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.