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 Everyone Lose Weight on Mounjaro?
No — not everyone loses weight on Mounjaro, and results vary significantly between individuals. Clinical trials showed average weight loss of 15–21% of body weight, but some people lose less, and some lose more. Success depends on dose, adherence, lifestyle changes, and individual metabolism. This guide explains what affects results, UK costs for private access, and how to access Mounjaro through the NHS or privately with a clinical assessment.
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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 Results: Why Individual Response Varies
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that works by reducing appetite and helping you feel fuller after smaller meals. In the SURMOUNT-1 clinical trial, participants on 15 mg lost an average of 20.9% of body weight over 72 weeks — alongside a reduced-calorie diet and increased physical activity. However, individual results vary considerably.
Factors affecting weight loss on Mounjaro include:
- Starting weight: People with higher starting weights sometimes see greater absolute weight loss
- Dose and titration: Most people require at least 10 mg to see meaningful results; the maximum dose is 15 mg once weekly
- Lifestyle adherence: Mounjaro works best alongside reduced-calorie diet and physical activity — it is not a standalone treatment
- Genetics and metabolism: Natural differences in how bodies respond to GLP-1 signalling affect outcomes
- Underlying health conditions: Type 2 diabetes, PCOS, or thyroid issues may affect weight loss response
- Medication interactions: Other medications can influence appetite regulation and weight loss
Some people experience minimal weight loss despite being on an appropriate dose. If this occurs, your prescriber may recommend dose escalation, lifestyle review, or discussion of alternative options. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses.
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.
Mounjaro Cost in the UK: NHS vs Private Access
NHS access: Mounjaro is approved by NICE for use in NHS specialist weight management services (tier 3/4), but access varies significantly by region. Many areas have long waiting lists or limited availability. Your GP can refer you to your local NHS weight management service, but you may wait several months.
Private access: Through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, Mounjaro typically costs £129–£320 per month depending on dose. Lower starting doses (2.5–5 mg) are cheaper than maintenance doses (10–15 mg). Private access is faster — usually 1–2 weeks from consultation to first injection. You'll complete an online health questionnaire, have a brief consultation with a prescriber, and if approved, receive your KwikPen by post. A one-year course costs approximately £1,550–£3,840 depending on dose progression.
Use our BMI calculator above to check your eligibility before pursuing either route.
NHS vs Private Comparison: NHS provides ongoing medical supervision and support but involves waiting and variable availability. Private access is faster and more assured but requires out-of-pocket cost. Both routes require a clinical assessment and prescription from a licensed healthcare professional. Once prescribed, you self-inject once weekly using a pre-filled KwikPen device. Storage requires a fridge (2–8°C unopened, up to 30 days at room temperature once started). Track your weight loss journey with our free progress tracker to monitor results over time.
- 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 work for me if it didn't work for someone else?
Yes — Mounjaro's effectiveness varies significantly between individuals. Just because someone else had minimal weight loss does not mean you will have the same outcome. Factors like dose, lifestyle adherence, genetics, and underlying health conditions all affect results. Your prescriber can assess your individual circumstances and recommend the best approach.
What dose of Mounjaro produces the most weight loss?
The maximum dose is 15 mg once weekly, which produced the greatest average weight loss (20.9%) in clinical trials. However, many people see good results at 10 mg, and side effects are often more manageable at lower doses. Your prescriber will recommend a starting dose (usually 2.5 mg) and escalate gradually every 4 weeks based on tolerance and response.
How long does it take to see weight loss results on Mounjaro?
Most people notice appetite suppression within the first 1–2 weeks, but measurable weight loss typically appears after 4–8 weeks. Significant results usually become apparent after 12–16 weeks of consistent use. Trial data measured weight loss over 72 weeks, so patience is important.
Can I get Mounjaro on the NHS quickly?
NHS availability varies significantly by region. Some areas have 6–12 month waiting lists for specialist weight management services. Your GP can refer you to assess eligibility, but private access through an online clinical assessment is faster — usually 1–2 weeks from consultation to first injection.
What happens if I stop using Mounjaro?
Weight typically returns gradually after stopping, as appetite regulation normalises. Most people regain weight within 6–12 months if they revert to previous eating patterns. Some people continue indefinitely; others use it for defined periods. Discuss long-term plans with your prescriber, and use a progress tracker to monitor changes.
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.