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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Mounjaro Testimonials vs Wegovy: What's the Difference?
When people search for Mounjaro testimonials online, many are also comparing it to Wegovy — the other major GLP-1 weight loss injection available in the UK. While both are prescription-only medicines that can support weight management, they work through different mechanisms and show different results in clinical trials. This guide compares the two factually, explains how they differ, and clarifies that prescriber assessment — not testimonials alone — determines which is right for you.
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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.
Clinical Trial Data and How Each Medicine Works
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. This means it activates two different hormone pathways in the body, which is why it may have a different effect profile compared to Wegovy.
Wegovy (semaglutide) is a GLP-1-only receptor agonist — it activates a single hormone pathway.
In the SURMOUNT-1 clinical trial, Mounjaro at the maximum dose of 15 mg showed an average weight loss of approximately 20.9% of body weight over 72 weeks. In the STEP-1 trial, Wegovy at 2.4 mg showed average weight loss of approximately 14.9% of body weight over 68 weeks. However, individual results vary significantly, and these are averages across clinical trial participants who also followed reduced-calorie diets and increased physical activity. Clinical trials also show that both medicines cause similar common side effects — nausea, diarrhoea, constipation, and stomach pain are typical, especially during dose escalation.
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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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Eligibility and How Your Prescriber Chooses
Both Mounjaro and Wegovy are available to UK adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Access is through NHS specialist tier 3 weight management services or private online prescribing following a clinical assessment.
Your prescriber will assess which medication — if either — is appropriate based on your medical history, current medications, and individual health profile. Neither testimonials nor trial averages determine suitability; clinical assessment does. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses with either medication, and our BMI calculator to confirm your current classification.
- 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 Mounjaro better than Wegovy based on testimonials?
Clinical trials show Mounjaro had slightly higher average weight loss than Wegovy, but individual results vary widely. Testimonials reflect one person's experience and are not reliable for predicting your own outcome. A prescriber's assessment of your health is far more important than online testimonials when choosing a medication.
Can you switch from Wegovy to Mounjaro if Wegovy isn't working?
Switching between medications is a clinical decision made with your prescriber. Approximate dose equivalences exist (Wegovy 2.4 mg ≈ Mounjaro 10–15 mg), but any switch must be managed by a healthcare professional. Do not attempt to switch on your own.
Are the side effects of Mounjaro and Wegovy the same?
Both medicines commonly cause nausea, diarrhoea, vomiting, and constipation — especially during dose escalation. Both can cause injection site reactions and fatigue. Serious side effects (pancreatitis, gallbladder problems, allergic reactions) are rare but possible with both. Your prescriber will discuss side effects relevant to your health profile.
Which injection costs more in the UK — Mounjaro or Wegovy?
Private costs vary by provider and dose, typically ranging from £129–£320 per month depending on which medication and dose you're prescribed. NHS costs depend on your regional ICB and specialist weight management service. Your prescriber will not choose based on cost alone — clinical suitability comes first.
How long does it take to see weight loss results with either medication?
Weight loss typically becomes noticeable within 4–8 weeks, with continued loss as you progress through dose escalations. Most of the trial weight loss occurred between weeks 8 and 52. Results depend on diet, activity level, and your individual metabolism — not just the medication itself.
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.