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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How Long Do You Stay On Mounjaro in the UK?
There's no fixed duration for Mounjaro treatment in the UK — the length of time you take it depends on your individual response, your GP's assessment, and whether you're accessing it through NHS specialist services or privately. The dose titration phase typically takes 16–20 weeks, but the overall treatment duration is personalised based on your progress and health goals. This guide explains NHS timelines, eligibility criteria, and what to expect when starting Mounjaro on the UK healthcare system.
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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.
Mounjaro Treatment Duration: NHS and UK Context
In the UK, there is no set end date for Mounjaro treatment — your prescriber will review your progress regularly and decide whether to continue based on your individual results and health status. The dose titration phase (escalating from 2.5 mg to your target dose) typically takes 16–20 weeks, with the minimum 4 weeks at each dose before increasing.
NHS guidance suggests that if you have not achieved meaningful weight loss after 12 weeks of treatment, the medication may not be suitable for you, and your prescriber will discuss stopping or alternatives. Clinical trials showed that continued use maintained weight loss, but many patients remain on Mounjaro long-term — there is no standard "stop date". Your GP or specialist will reassess you regularly, typically every 3–6 months, to evaluate whether to continue, adjust the dose, or discuss stopping.
- Weeks 1–4: 2.5 mg injection (starting dose)
- Weeks 5–8: 5 mg (first escalation)
- Weeks 9–12: 7.5 mg (if tolerated)
- Weeks 13–16: 10 mg (if tolerated)
- Weeks 17–20: 12.5 mg or 15 mg (maximum dose)
- Ongoing: Regular review every 3–6 months to assess continued benefit and tolerability
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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 Access: Duration and Continuity
NHS route: If you're prescribed Mounjaro through a specialist tier 3 weight management service, your treatment is managed and monitored through the NHS. You'll have scheduled reviews, and your prescriber will decide on duration based on clinical progress. However, NHS access is limited and varies significantly by region — waiting lists can be months or years in some areas.
Private route: Those accessing Mounjaro privately through UK-licensed prescribers have more flexibility — you can continue treatment as long as you wish, provided you remain eligible and have ongoing clinical assessments. Private prescribers typically require 3–6 monthly check-ins to renew your prescription. Use our GLP-1 weight loss calculator to project your potential results at different doses, which can help guide your discussions with your prescriber about treatment goals and duration.
When weight loss plateaus or stops, your prescriber may suggest increasing your dose (if you're not already on 15 mg) or reassessing your overall plan. Some patients benefit from a "drug holiday" (temporary break) before restarting — this is a clinical decision made with your prescriber. Stopping Mounjaro suddenly is safe, but weight regain is common without sustained lifestyle changes. Your prescriber will help you plan for maintenance or stopping, and your GLP-1 calculator results can be tracked over time using our free progress tracker to visualise your journey.
- 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 long does the Mounjaro dose titration phase take in the UK?
The dose titration phase typically takes 16–20 weeks. You spend a minimum of 4 weeks on each dose (starting at 2.5 mg, escalating every 4 weeks) before reaching your target maintenance dose, usually 10 mg or 15 mg. Your prescriber may adjust this timeline based on your tolerability and response.
Is there a time limit on how long I can take Mounjaro on the NHS?
No set time limit exists. The NHS will continue your prescription as long as it's clinically appropriate and you're achieving meaningful weight loss. Your specialist team will review you every 3–6 months and decide whether to continue, adjust, or stop based on your progress.
What happens if I don't lose weight after 12 weeks on Mounjaro?
If you haven't seen meaningful weight loss after 12 weeks, your prescriber will discuss whether Mounjaro is working for you. They may increase your dose, review your diet and exercise, or consider stopping and trying an alternative approach. Every person responds differently to treatment.
Can I take Mounjaro long-term, or is it only short-term treatment?
Mounjaro is not time-limited — many patients take it long-term to maintain weight loss. Some take it for 1–2 years; others continue indefinitely. The decision is made between you and your prescriber based on your goals, tolerability, and continued benefit. Stopping is always an option if you wish to do so.
What's the difference between NHS and private Mounjaro treatment duration?
NHS duration is managed by specialist services with regular reviews; continuity depends on NHS availability in your region. Private prescribing offers more flexibility — you can continue as long as you remain eligible and maintain clinical assessments, typically every 3–6 months. Both routes require ongoing prescription and monitoring.
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.