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
How Long Do People Stay On Mounjaro?
There's no fixed time limit for staying on Mounjaro (tirzepatide) — treatment duration varies significantly between individuals based on your health goals, personal response, and prescriber guidance. Some people may continue long-term, whilst others might take a break after reaching their target weight. Unlike some medications that have a set course, GLP-1 medications are designed to be used as long as they're helping and remain clinically appropriate for you. Your GP or prescriber will monitor your progress and discuss ongoing suitability regularly.
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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 vs Wegovy: Duration and Continuation
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only GLP-1 medications designed for long-term weight management rather than short-term courses. In clinical trials, participants used both medications for extended periods: SURMOUNT-1 (Mounjaro) ran for 72 weeks with participants continuing at their maintenance dose, whilst STEP-1 (Wegovy) showed continued weight loss benefits at 68 weeks. The key difference in mechanism — Mounjaro's dual GIP+GLP-1 action versus Wegovy's single GLP-1 pathway — doesn't determine how long you stay on either medication. Instead, your prescriber will assess whether you're experiencing meaningful health benefits, whether side effects are manageable, and whether your motivation to continue treatment aligns with your health goals. Some people stay on Mounjaro or Wegovy indefinitely; others may pause or discontinue after reaching target weight. Individual suitability is what matters most, not a predetermined endpoint.
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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.
Staying On or Stopping: What You Need To Know
If you're considering how long to stay on Mounjaro, the decision depends on several factors: how much weight you've lost, whether you've reached a meaningful health target (like improved blood sugar or blood pressure), how you're managing side effects, and your personal preference about continuing injections. Many people find that staying on a lower maintenance dose of Mounjaro — such as 5mg or 7.5mg — helps prevent weight regain, whilst others successfully transition to lifestyle management alone. Your prescriber will discuss realistic expectations before starting: weight loss is usually gradual, individual results vary significantly, and stopping suddenly may lead to gradual weight regain. Use our free BMI calculator to track your progress alongside your prescriber's assessments, and our GLP-1 weight loss calculator can help you understand potential outcomes at different doses. The "right" duration is whatever supports your long-term health — there's no one-size-fits-all timeline.
- 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.
Do you have to stay on Mounjaro forever?
No. Mounjaro is designed for long-term use but not necessarily indefinitely. Your prescriber will regularly assess whether treatment is still beneficial and appropriate for you. Some people continue long-term; others pause after reaching their health goals. Duration depends on individual response, side effects, and your preference. Always discuss any plans to stop with your GP or prescriber.
What happens if you stop taking Mounjaro?
Weight loss may gradually reverse if you return to previous eating habits — this is common with many weight management treatments. Your prescriber will advise you on the best way to discontinue (some people step down doses gradually rather than stop abruptly). Lifestyle changes made during treatment often help minimise rapid regain. Discuss transition plans with your prescriber before stopping.
Is Mounjaro a lifetime medication like type 2 diabetes injections?
Mounjaro is primarily prescribed for weight management rather than as a lifelong disease treatment like diabetes insulins. However, if you've regained weight previously or have weight-related health conditions, ongoing treatment may be appropriate. This is an individual decision made between you and your prescriber based on your specific health needs.
How does Mounjaro duration compare to Wegovy?
Both medications have similar treatment timelines — they're designed for long-term use with no fixed endpoint. Clinical trials ran both for around 68–72 weeks. The difference isn't in how long you stay on either drug, but in individual suitability, side effects, and your prescriber's assessment. Some people do better on one than the other.
Can you take a break from Mounjaro and restart later?
Potentially, yes — but always discuss this with your prescriber first. Some people take breaks and restart; others find continuous treatment works better for them. Weight often returns during breaks, and restarting requires a new clinical assessment. Your prescriber will advise what's safest and most effective for your specific situation. ```
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.