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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Why Is Wegovy Dose Lower Than Mounjaro?
Wegovy (semaglutide) and Mounjaro (tirzepatide) are both prescription-only weight management injections available in the UK, but they work differently—and their dosing reflects this. Wegovy's maximum dose is 2.4mg weekly, while Mounjaro goes up to 15mg weekly. This difference isn't a weakness of Wegovy; it's because these medications have different mechanisms of action. Understanding why can help you discuss which option might be suitable for you with your prescriber.
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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 These Medications Work Differently
Wegovy (semaglutide) is a single-mechanism GLP-1 receptor agonist. It activates one hormone pathway—GLP-1—which helps reduce appetite, support feelings of fullness, and slow gastric emptying. Because it targets one system, clinical trials found that semaglutide reaches an effective plateau at 2.4mg per week.
Mounjaro (tirzepatide) is a dual-mechanism medication—it activates both GIP and GLP-1 receptor pathways simultaneously. This dual action may provide a more powerful combined effect on appetite regulation and metabolism. Because it engages two hormone systems, higher doses can be tolerated and may offer additional benefit. The maximum of 15mg reflects this dual-action profile.
In clinical trials, Mounjaro demonstrated slightly higher average weight loss (~21% body weight) compared to Wegovy (~15% body weight). However, individual results vary significantly, and what works best depends on your personal health, medical history, and how your body responds.
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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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Comparing Dose Strength and Clinical Evidence
It's important not to equate dose numbers directly—2.4mg of semaglutide is not "weaker" than 15mg of tirzepatide; they're different compounds with different potencies. The dose ranges reflect each medication's pharmacology, not a hierarchy of strength.
Clinical evidence: Both medications are licensed in the UK for weight management in adults with a BMI of 30 or above (or 27+ with weight-related health conditions). STEP trial data showed Wegovy's effectiveness, whilst SURMOUNT trials demonstrated Mounjaro's results. Both are prescription-only and require a clinical assessment before prescribing. Your GP or a licensed prescriber will discuss which option—if either—is appropriate for your individual circumstances.
- 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 more powerful than Wegovy because the dose is higher?
Not necessarily. Mounjaro and Wegovy are different compounds with different potencies and mechanisms. Mounjaro's higher numerical dose reflects its dual GIP+GLP-1 action, whilst Wegovy's single GLP-1 mechanism reaches effectiveness at lower doses. Clinical trial results show Mounjaro achieved slightly higher average weight loss, but individual outcomes vary. A prescriber will assess which is more suitable for you.
Can Wegovy doses be increased beyond 2.4mg?
No. 2.4mg is the maximum approved dose for Wegovy in the UK. Once you reach this dose, it is typically maintained. If a higher dose is clinically needed, a prescriber might consider Mounjaro instead, but this is an individual decision based on your response and health profile.
Why does Mounjaro reach 15mg if it's just a weight loss injection?
Mounjaro's higher maximum dose reflects its dual-mechanism design—it activates both GIP and GLP-1 pathways. This allows for higher doses whilst maintaining safety. The dose titration schedule takes 20 weeks to reach 15mg, with at least four weeks between increases, ensuring your body adjusts gradually.
Which medication should I choose—Wegovy or Mounjaro?
This is a decision between you and your prescriber based on your medical history, any contraindications, preference for once-weekly injection frequency, and other personal factors. Both are effective prescription-only medications. Use our free GLP-1 weight loss calculator to explore potential outcomes, and discuss both options with your GP or licensed prescriber.
Are there other semaglutide products I should know about?
Yes—Ozempic also contains semaglutide but is approved for type 2 diabetes (maximum 2mg weekly) and is not licensed for weight management in the UK. Wegovy is the licensed weight management version at 2.4mg. Never use diabetes medications off-label for weight loss. Always use a prescription medication exactly as prescribed by your healthcare provider.
Ready to take control of your weight loss journey?
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