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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10mg Mounjaro Not Working — How Does It Compare to Wegovy?
If you're on 10mg Mounjaro and not seeing the weight loss results you expected, you're not alone — individual responses to GLP-1 and GIP/GLP-1 medications vary significantly. This guide compares Mounjaro (tirzepatide) with Wegovy (semaglutide) to help you understand the clinical evidence, mechanism differences, and why your prescriber might consider a switch or dose adjustment. Both are prescription-only weight management injections licensed in the UK, but they work in different ways. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses of each medication.
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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.
SURMOUNT vs STEP Trial Data — What the Clinical Evidence Shows
If 10mg Mounjaro isn't delivering expected results, it's helpful to understand how it compares to Wegovy based on clinical trial data. In the SURMOUNT-1 trial, participants on 10mg tirzepatide lost an average of 19.5% of body weight over 72 weeks alongside reduced-calorie diet and increased physical activity. By comparison, Wegovy's STEP-1 trial showed average weight loss of 14.9% of body weight at the maximum 2.4mg dose over 68 weeks under similar lifestyle conditions.
This suggests Mounjaro may support greater average weight loss, but individual responses vary considerably. Some people respond excellently to Mounjaro at lower doses, whilst others see minimal results even at maximum dose. Conversely, some individuals respond very well to Wegovy despite lower average trial outcomes. Clinical trial averages do not predict individual outcomes — your personal response depends on genetics, metabolism, adherence, lifestyle factors, and how your body's GLP-1 and GIP receptors respond to these medicines.
Your prescriber may consider: increasing your Mounjaro dose further (if not yet at 15mg), ensuring you're following reduced-calorie diet and exercise guidelines, checking for medication interactions, or exploring whether a different medication might suit you better.
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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
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Mechanism Differences — GLP-1 Only vs Dual GIP+GLP-1
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 work together to regulate appetite, satiety, and fat utilisation. This dual mechanism is why Mounjaro showed higher average weight loss than Wegovy in clinical trials.
Wegovy (semaglutide) is a GLP-1-only receptor agonist, activating a single hormone pathway. This single mechanism is still effective for weight management, but may produce different results in different people. Some individuals respond better to a single mechanism, whilst others benefit more from dual activation. If you've not seen results on 10mg Mounjaro, this doesn't automatically mean Wegovy will work better — the issue may be dose, lifestyle factors, or individual suitability. Always discuss any medication change with your prescriber, who can assess your individual response and health context before recommending a switch.
- 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.
Why isn't 10mg Mounjaro working for me when trials show good results?
Clinical trial results are averages — not everyone responds the same way. Individual weight loss depends on genetics, metabolism, lifestyle adherence, existing health conditions, and how your body's receptors respond to the medicine. Your prescriber may recommend dose increase, lifestyle review, or exploring alternative medications based on your specific situation.
Is Wegovy better than Mounjaro if Mounjaro isn't working?
Not necessarily. Wegovy showed lower average weight loss in trials (14.9% vs 19.5% for Mounjaro at maximum doses). If Mounjaro hasn't worked, the issue may not be the medication type itself but dose, lifestyle factors, or individual suitability. Your prescriber will assess which option suits you best.
Should I switch from Mounjaro to Wegovy?
Only your prescriber can advise this. Switching medications is a clinical decision based on your individual response, health history, and preferences. Some people do respond better to Wegovy; others see improved results by increasing Mounjaro dose or adjusting lifestyle factors. Discuss all options with your GP or specialist.
What's the approximate Mounjaro to Wegovy conversion dose?
Approximate equivalents are: 10mg Mounjaro ≈ 1.7mg Wegovy, and 15mg Mounjaro ≈ 2.4mg Wegovy. These are not official conversions — prescribers may start at different doses depending on your individual response. Any medication switch must be managed by your prescriber.
What if neither Mounjaro nor Wegovy work for me?
Other options include Saxenda (liraglutide, a daily GLP-1 injection), lifestyle intensification, or referral to tier 3/4 NHS specialist services if you haven't accessed these. Your GP can discuss all available options for sustained weight management based on your health context and previous responses.
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.