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 Take Mounjaro in the UK?
Mounjaro (tirzepatide) is a prescription-only weight management injection used long-term in the UK, typically started through NHS specialist tier 3 services or private prescription. There is no fixed end date—treatment duration depends on your individual health, weight loss progress, and whether you maintain your results. Most people take Mounjaro for months to years, with dose escalation every 4 weeks until reaching an effective maintenance dose. Your GP or prescriber will review your treatment regularly to assess whether to continue, pause, or adjust your approach.
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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.
How Long Do You Stay on Mounjaro? NHS Duration and Escalation
Unlike short-term weight loss programmes, Mounjaro is designed as a long-term treatment. You don't simply take it for a fixed number of weeks and stop. Instead, treatment duration is personalised based on your clinical response and health goals. The NHS and NICE recognise Mounjaro as part of tier 3 specialist weight management services, meaning access is through specialist multidisciplinary teams rather than routine GP prescription. Dose titration follows a structured schedule: you start at 2.5 mg once weekly for 4 weeks, then increase by 2.5 mg every 4 weeks (5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg maximum) until reaching an effective maintenance dose. Most people remain on their maintenance dose for 6–12 months or longer, with regular clinical review every 3–6 months to assess weight loss progress, side effects, and whether to continue.
- Starting dose: 2.5 mg weekly for 4 weeks
- Escalation schedule: Increase by 2.5 mg every 4 weeks up to maximum 15 mg
- Minimum time per dose: 4 weeks before escalating
- Typical treatment duration: 6 months to several years with ongoing review
- Review intervals: Every 3–6 months with your prescriber or specialist service
Clinically BackedWeight Loss
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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 Treatment Duration
NHS route: If you access Mounjaro through an NHS tier 3 specialist weight management service, your treatment plan is reviewed by a multidisciplinary team including dietitians, psychologists, and physicians. Treatment duration depends on NHS service guidance and your clinical response. Waiting lists for NHS specialist services vary significantly by region (ICB), and treatment may be paused or reviewed if you reach weight loss targets or experience side effects. Private route: Those prescribed through private online consultations with a UK-licensed prescriber can typically continue treatment as long as they wish, provided they remain eligible (healthy enough to continue) and clinical reviews remain positive. Regardless of route, your prescriber should recommend stopping or pausing Mounjaro if you're not achieving meaningful weight loss after 6 months, or if side effects outweigh benefits. Using our GLP-1 weight loss calculator above can help you project potential outcomes at different doses.
- 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.
Does Mounjaro stop working over time?
Some people experience weight loss plateaus after several months, which is normal—your body adapts to the medication. Your prescriber may increase your dose (if not already at maximum) or review your diet and activity levels. This is why regular clinical review every 3–6 months matters. Continuing Mounjaro typically helps maintain weight loss even if progress slows.
What happens when you stop taking Mounjaro?
If you stop Mounjaro, appetite-suppressing effects generally wear off within 1–2 weeks. Most people regain some weight over time if diet and activity levels don't change permanently. This is why lifestyle changes alongside medication are essential. Your prescriber will discuss stopping gradually rather than abruptly if you've been on it long-term.
Can you take Mounjaro forever?
Yes, Mounjaro can be taken long-term if clinically appropriate and effective. Weight management is often a lifelong process. The medication is not habit-forming. However, your prescriber will regularly assess whether continuing is right for you based on weight loss results, side effects, and overall health. Costs and access may also influence duration.
How long until you see results from Mounjaro?
Most people notice reduced appetite within 1–2 weeks of starting. Measurable weight loss typically begins within 4–8 weeks. Clinical trials showed an average of 15–clinically studied weight loss over 72 weeks at maximum dose, though individual results vary significantly. Your BMI calculator can track your baseline, and our progress tracker helps log weekly changes.
What's the difference between Mounjaro and Wegovy treatment duration?
Both are long-term medications with no fixed end date. Mounjaro is a dual GIP/GLP-1 agonist (up to 15 mg weekly), while Wegovy is a GLP-1 agonist only (up to 2.4 mg weekly). Both require regular clinical review. Mounjaro vs Wegovy choice depends on individual health factors, prescriber recommendation, and access—not on treatment length, which is similar for both.
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.