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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Maintenance on Mounjaro vs Wegovy — What You Need to Know
If you're considering long-term weight management with prescription injection therapy, understanding how Mounjaro and Wegovy work during the maintenance phase is essential. Both medications are licensed for weight management in UK adults, but they differ in mechanism, dosing, and how they're maintained once you reach your target weight. This guide compares the two based on clinical evidence and UK prescribing guidelines.
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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.
How Maintenance Differs Between Mounjaro and Wegovy
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. The maintenance dose is typically 15 mg once weekly, the maximum approved dose in the UK. You reach this through dose titration over approximately 20 weeks, starting at 2.5 mg and increasing every 4 weeks if tolerated. Once you're stable at your maintenance dose, you continue the same injection each week for ongoing weight management.
Wegovy (semaglutide) is a GLP-1-only receptor agonist with a maximum maintenance dose of 2.4 mg once weekly. The titration schedule is longer, typically 16–17 weeks, starting at 0.25 mg. Like Mounjaro, once you reach 2.4 mg, you stay on that dose for continued management. Clinical trial data from the STEP studies showed average weight loss of approximately 15% body weight at the 2.4 mg maintenance dose, whilst Mounjaro's SURMOUNT trial demonstrated average weight loss of 15–21% at 15 mg maintenance—though individual results vary significantly.
The key mechanism difference is that Mounjaro's dual action on GIP and GLP-1 may offer different appetite regulation than Wegovy's single GLP-1 pathway. However, both work best alongside reduced-calorie diet and increased physical activity.
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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.
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Choosing Between Them — What Your Prescriber Will Consider
Both medications are prescription-only and require clinical assessment before starting. Your GP or a licensed prescriber will assess your individual health, BMI, weight-related conditions, and medication history to determine which is more suitable. Neither is inherently "better"—suitability depends on your personal health profile, any existing medications that might interact, and how your body responds during the initial treatment phase.
If you're already on one medication and considering a switch to the other, this must be managed by your prescriber. There's no official established conversion chart between Mounjaro and Wegovy doses, though approximate equivalences are used in clinical practice. Some prescribers may recommend staying on your current medication if it's working well, whilst others may trial a switch based on tolerability or clinical response. Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different doses, and always discuss maintenance expectations with your prescriber before starting.
- 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.
What's the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) is a GLP-1-only agonist. This means Mounjaro activates two natural hormone pathways for appetite regulation, potentially offering a different mechanism. Both are once-weekly injections licensed for weight management in the UK.
What's the maintenance dose for each?
Mounjaro maintenance is typically 15 mg once weekly (the maximum UK-approved dose). Wegovy maintenance is 2.4 mg once weekly. Both require titration over several months before reaching maintenance, and both are prescription-only medicines requiring clinical assessment.
Which causes more weight loss — Mounjaro or Wegovy?
Clinical trials showed Mounjaro resulted in average weight loss of 15–21% body weight, whilst Wegovy showed approximately 15% at the maximum dose. However, individual results vary significantly. Your prescriber will advise based on your personal health and suitability—neither is assured to work the same for everyone.
Can I switch from Wegovy to Mounjaro during maintenance?
Yes, but only under prescriber guidance. There's no official conversion chart between the medications. If you're thinking about switching, discuss it with your GP or prescriber—they may recommend staying on your current medication if it's working well for you.
How long do I stay on maintenance doses?
Weight management with these medications is typically long-term. Once you reach your target weight and maintenance dose, you'll usually continue the same weekly injection to sustain your weight loss. If you stop, weight may return—discuss duration and long-term plans with your prescriber before starting.
Ready to take control of your weight loss journey?
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