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 Can You Take Mounjaro? UK NHS Guidance
Mounjaro (tirzepatide) is approved for long-term weight management in UK adults, but how long you can continue the injection depends on your individual response and NHS or private prescribing criteria. Unlike short-term diet plans, Mounjaro is designed as an ongoing treatment — though the duration varies from person to person. This guide covers NHS prescribing timelines, how the kwikpen injection schedule works over months and years, and what to expect from sustained use of this dual GIP and GLP-1 receptor agonist medication.
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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.
NHS Long-Term Prescribing and Treatment Duration
Mounjaro is not approved as a time-limited treatment in the UK — meaning there is no official maximum duration set by MHRA or NICE. However, NHS prescribing follows these practical principles:
- Initial assessment and titration (weeks 1–20): Your prescriber will escalate your dose from 2.5 mg up through the standard dosing schedule. This period is when your body adjusts and your prescriber confirms the medication is working and tolerated.
- Maintenance phase (weeks 21 onwards): Once you reach an effective dose (typically 10 mg or 15 mg), you continue the once-weekly kwikpen injection indefinitely, as long as it is helping and you remain eligible.
- Ongoing monitoring: NHS tier 3 specialist weight management services typically review you at 12 weeks, 6 months, and annually. Private prescribers also review regularly to assess continued suitability.
- Eligibility review: If your weight or health circumstances change significantly, your prescriber may reassess whether continued Mounjaro remains the right choice. Access through NHS specialist services may also depend on regional ICB capacity.
The key difference from short-term dieting: Mounjaro is an ongoing medication, not a temporary intervention. Clinical evidence suggests that weight regain often occurs within months of stopping GLP-1 medications, so sustained use is part of the treatment plan for most people.
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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.
Stopping Mounjaro and Weight Regain Risk
If you stop taking Mounjaro, your appetite signals typically return to pre-treatment levels within days to weeks. Research indicates that people who discontinue GLP-1 medications like tirzepatide or semaglutide (Wegovy) often regain weight — sometimes more than they had lost — within 6 months.
This is why long-term use is considered the standard approach for people who have successfully lost weight on Mounjaro. Your GP or specialist prescriber can discuss with you whether continuing indefinitely, tapering gradually, or planning for future management of weight makes sense for your specific situation. Some people may switch to lifestyle maintenance if they have achieved stable weight loss and sustainable habits. Use our GLP-1 weight loss calculator to estimate your personal weight loss trajectory and discuss long-term goals with your prescriber.
- 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.
Can you take Mounjaro long term on the NHS?
Yes, Mounjaro can be prescribed long term on the NHS through tier 3 specialist weight management services, with no set maximum duration. However, NHS access and continuation depend on your region (ICB availability), ongoing weight loss or maintenance, and continued eligibility. You will have regular reviews, typically at 12 weeks, 6 months, and annually.
What happens to your weight when you stop Mounjaro?
When Mounjaro is stopped, appetite usually returns to pre-treatment levels within days to weeks. Research shows most people regain weight within 6 months, sometimes exceeding their initial loss. This is why long-term use is standard practice for people who want to maintain weight loss achieved with tirzepatide.
How long does it take Mounjaro to work?
Most people notice reduced appetite within the first 2–4 weeks of starting Mounjaro at 2.5 mg, though significant weight loss typically begins after 4–8 weeks as your dose is increased. The full effect is usually seen by weeks 12–16 at a stable maintenance dose, following the standard dose titration schedule.
Is Mounjaro safe to use for years?
Mounjaro has not been studied for longer than approximately 2 years in clinical trials (SURMOUNT-1 ran for 72 weeks). However, MHRA approval indicates it is safe for ongoing use in eligible patients. Long-term real-world safety data is still being gathered. Your prescriber will monitor you regularly and can discuss any individual concerns.
What is the difference between Mounjaro and Wegovy for long term use?
Both Mounjaro (tirzepatide, dual GIP+GLP-1) and Wegovy (semaglutide, GLP-1 only) are designed for long-term weight management with no official end date. Mounjaro may produce slightly greater weight loss on average (~20% vs ~15%), but both require ongoing use to maintain results. Your prescriber will recommend the most suitable option based on your health profile and response.
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.