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
Looking for a cheaper alternative to Mounjaro in the UK?
If you're considering prescription weight loss treatment in the UK, Wegovy (semaglutide) is often compared to Mounjaro (tirzepatide) as a cost alternative. Both are once-weekly injectable medications licensed for weight management in UK adults. While they work differently and have different dose ranges, both require a clinical assessment and prescription. This guide explains the key differences to help you understand your options when discussing weight loss treatment with your GP or a licensed prescriber.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Mounjaro and Wegovy compare: mechanism, doses, and trial data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways to regulate appetite and blood sugar. It starts at 2.5 mg and escalates to a maximum of 15 mg once weekly. In the SURMOUNT-1 clinical trial, participants on the highest dose (15 mg) lost an average of approximately 20.9% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. It starts at 0.25 mg and escalates to a maximum of 2.4 mg once weekly. In the STEP-1 clinical trial, participants lost an average of approximately 14.9% of body weight at 68 weeks on the 2.4 mg maintenance dose, also with lifestyle changes.
Both medications slow how quickly food leaves the stomach and help reduce appetite. The dual mechanism of Mounjaro may account for the slightly higher average weight loss shown in trials, though individual results vary significantly. Try our GLP-1 weight loss calculator to explore projected outcomes at different doses.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Cost in the UK: private pricing and availability
In the UK, both Mounjaro and Wegovy are available through NHS specialist weight management services (waiting times vary significantly by region) and through private online prescribing. Private costs typically range from £129–£320 per month depending on the dose, with both medications generally priced similarly. Some patients find Wegovy slightly cheaper at lower doses, whilst Mounjaro at standard maintenance doses may cost slightly more due to higher doses per injection. However, pricing varies between providers, so comparing current costs directly with prescribers is essential. Both require a clinical assessment before prescription. Your GP can also advise on NHS eligibility and referral to specialist services in your area.
The choice between Mounjaro and Wegovy depends on individual suitability, not just cost. A prescriber will assess your medical history, any existing conditions, current medications, and weight loss goals to recommend which is appropriate for you. Neither is universally "better" — clinical trials show both are effective, and individual response varies. Using our BMI calculator can help you understand your current weight classification and provide context when discussing options 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.
Is Wegovy cheaper than Mounjaro in the UK?
Both typically cost similar amounts privately in the UK, ranging from £129–£320 monthly depending on dose. Wegovy may be slightly cheaper at lower doses, whilst Mounjaro at higher doses may cost more. Always compare current pricing with specific prescribers, as costs vary between providers.
What's the main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist (two hormone pathways), whilst Wegovy is a GLP-1 receptor agonist only (one pathway). This gives Mounjaro a dual mechanism, which may contribute to slightly higher average weight loss in clinical trials, though individual results vary significantly.
Which medication showed better weight loss results in trials?
Mounjaro (SURMOUNT-1 trial) showed average weight loss of approximately 20.9% at the maximum 15 mg dose, whilst Wegovy (STEP-1 trial) showed approximately 14.9% at 2.4 mg. Both achieved results alongside reduced-calorie diet and increased physical activity. Individual outcomes vary considerably.
Can my GP prescribe Mounjaro or Wegovy on the NHS?
Both are available through NHS specialist tier 3 weight management services following referral from your GP. Availability and waiting times vary significantly by region (ICB). Private prescribing is also available without NHS referral through UK-licensed online prescribers.
How do I know which medication is right for me?
A prescriber will assess your individual health profile, BMI, any weight-related conditions, current medications, and allergies to determine suitability. Neither medication is universally better — both are effective for appropriate candidates. Your prescriber will recommend based on your specific circumstances, not cost alone.
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.