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 Can You Stay On Mounjaro?
There's no set time limit for how long you can stay on Mounjaro (tirzepatide) in the UK — treatment duration depends on your individual health needs and how well the medication works for you. Most people continue Mounjaro as long as it's helping with weight management and your GP or prescriber agrees it remains appropriate. The NHS and NICE guidance focus on regular monitoring rather than stopping at a specific date, meaning you could potentially stay on it indefinitely if it continues to be effective and safe for your circumstances.
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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 Prescribing Duration and Monitoring Requirements
The NHS has no fixed time limit for Mounjaro prescriptions — your prescriber will review your treatment regularly to ensure it remains suitable. NICE guidance emphasises that weight loss medications should continue as long as they are effective and well-tolerated. This typically means:
- Regular GP or specialist reviews (usually every 3–6 months) to assess weight loss progress and side effects
- Assessment of whether the tirzepatide dose needs adjusting or if weight loss has plateaued
- Monitoring for any new health concerns that might make continuation unsuitable
- Evaluation of whether lifestyle changes (diet and exercise) are being maintained alongside the medication
If you stop Mounjaro, weight regain is common — typically 50–75% of lost weight returns within a year if no lifestyle changes continue. This is why NHS guidance treats weight management medications as potentially long-term rather than short-term interventions. Your prescriber will balance the benefits of continued weight loss against any side effects you're experiencing and your individual health goals.
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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.
Duration Differences: NHS vs Private Prescribing
On the NHS through tier 3 specialist services, Mounjaro is prescribed as part of a multidisciplinary weight management programme, and duration is individualised based on your response and needs — there's no automatic end date. However, NHS availability varies significantly by region, and waiting lists can be lengthy.
Private prescribing (through GPhC-registered online services) follows the same clinical principles — no fixed time limit — but reviews are typically conducted more frequently (monthly or every 3 months) to ensure safety and continued suitability. Whether NHS or private, you can potentially continue Mounjaro for years if it remains effective. Using our GLP-1 weight loss calculator can help you track potential progress and discuss realistic goals with your prescriber during reviews.
- 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 I stay on Mounjaro forever?
Potentially, yes — if the medication continues to help you lose weight, side effects remain manageable, and your prescriber agrees it's appropriate. However, regular reviews are essential. Many people may reach a maintenance phase where they stay on a stable dose long-term rather than continuing dose increases. Discuss long-term plans with your GP or specialist prescriber.
What happens if I stop Mounjaro?
Most people regain weight after stopping — typically 50–75% of lost weight returns within a year. This is why NHS guidance treats weight loss medications as potentially ongoing. If you're considering stopping, discuss with your prescriber about transitioning to maintenance or alternative approaches to prevent regain.
How often will the NHS review my Mounjaro prescription?
Reviews typically happen every 3–6 months through NHS tier 3 services, though this varies by region. Your prescriber will assess weight loss progress, side effects, any health changes, and whether continuation remains appropriate. Private prescribers often review more frequently.
Does NICE say how long I can take Mounjaro?
No — NICE guidance doesn't set a maximum duration. Instead, NICE recommends continuing weight loss medications (including tirzepatide) as long as they're effective, well-tolerated, and you're maintaining lifestyle changes. Decision to continue is based on individual benefit and safety.
Will my GP continue prescribing Mounjaro long-term?
This depends on your response and whether your GP feels it's appropriate. Some people stay on Mounjaro for years; others may move to maintenance or stop after reaching their goal. Use our free BMI calculator and progress tracker to monitor your results and discuss long-term plans during your regular reviews with your prescriber.
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.