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
Is Mounjaro Stronger Than Wegovy?
The short answer: Mounjaro and Wegovy work differently, so "stronger" isn't quite the right comparison. Mounjaro (tirzepatide) uses a dual mechanism affecting two hormone pathways, while Wegovy (semaglutide) targets one. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but individual results vary significantly. Both are prescription-only medications in the UK requiring clinical assessment. The right choice depends on your personal health profile, not which one is "stronger."
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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 Mounjaro and Wegovy Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways in the body simultaneously. This dual action may help regulate appetite more effectively across different mechanisms. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. Both slow how quickly food leaves your stomach and signal fullness to your brain, but the dual mechanism in Mounjaro theoretically offers an additional lever for weight management.
In the SURMOUNT clinical trial, Mounjaro at the maximum dose of 15 mg produced an average weight loss of approximately 20.9% of body weight over 72 weeks. In the STEP clinical trials, Wegovy at its maximum dose of 2.4 mg produced average weight loss of approximately 14.9% over 68 weeks. These are trial averages — actual results vary widely between individuals, and both medications work best alongside a 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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Dosing, Side Effects, and Practical Differences
Mounjaro starts at 2.5 mg and escalates to a maximum of 15 mg once weekly. Wegovy starts at 0.25 mg and escalates to 2.4 mg once weekly — a much lower dose range. Both are once-weekly injections in a pre-filled pen. Side effects are similar for both medications: nausea, diarrhoea, constipation, and stomach pain are common, especially during dose escalation. Neither is "stronger" in terms of side effect severity — tolerability is individual. For UK access, both are prescription-only. NHS availability is through tier 3 specialist weight management services; private access is through online prescribing following clinical assessment. Use our GLP-1 weight loss calculator to explore how either medication might fit your health goals.
- 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 cause more side effects than Wegovy?
Both medications cause similar side effects — nausea, diarrhoea, constipation, and stomach pain are common during dose escalation. Individual tolerance varies. Neither is consistently "worse" than the other. Your prescriber will monitor side effects and adjust dosing if needed.
Which medication produces faster weight loss?
Mounjaro showed slightly higher average weight loss in clinical trials (20.9% vs 14.9%), but these are population averages. Individual results vary significantly based on genetics, diet, activity level, and adherence. Some people respond better to one than the other.
Can I switch from Wegovy to Mounjaro on the NHS?
NHS switching between these medications depends on your local tier 3 specialist service and NICE guidance. Your specialist team will advise if a switch is appropriate for your situation. Private prescribers can also assess eligibility for either medication.
Is Mounjaro available on the NHS?
NICE has approved tirzepatide (Mounjaro) for NHS use within tier 3 specialist weight management services. However, regional availability varies significantly, and waiting lists can be long. Your GP can refer you to your local service for assessment.
Which medication is cheaper in the UK?
Both Mounjaro and Wegovy are available privately at similar price ranges (roughly £129–£320 per month depending on dose). NHS access is free but subject to regional availability and service capacity. Cost should not be your primary deciding factor — clinical suitability matters more.
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.