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 Clicks vs Wegovy: Dose and Mechanism Explained
If you're considering weight loss injections in the UK, you've likely heard of both Mounjaro and Wegovy. While both are prescription-only GLP-1 medications approved for weight management, they work differently and use different dosing schedules. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist delivered via KwikPen clicks, whilst Wegovy (semaglutide) is a GLP-1-only agonist with its own injection system. Understanding the differences between their doses and mechanisms can help you discuss options with your GP or 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 Mounjaro and Wegovy Dosing Compare
Mounjaro uses a pre-filled KwikPen device that delivers doses in 2.5 mg increments, starting at 2.5 mg once weekly and escalating to a maximum of 15 mg. Each click on the pen represents a specific dose — the prescriber tells you how many clicks to use each week. The dose increases every 4 weeks if tolerated, offering five distinct dose levels (2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg).
Wegovy uses a different injection pen and follows a more gradual escalation: starting at 0.25 mg and increasing through 0.5 mg, 1 mg, 1.7 mg, and reaching a maximum of 2.4 mg once weekly. Wegovy's lowest starting dose (0.25 mg) is significantly lower than Mounjaro's 2.5 mg, which may affect how quickly side effects appear.
Key mechanism difference: Mounjaro is a dual GIP + GLP-1 agonist, activating two hormone pathways. Wegovy activates GLP-1 only. This dual action may explain Mounjaro's slightly higher average weight loss in SURMOUNT trials (approximately 15–21% body weight) compared to Wegovy's STEP trial results (approximately 14.9%).
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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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Clinical Evidence and Individual Suitability
The SURMOUNT-1 trial showed Mounjaro at 15 mg resulted in average weight loss of approximately 20.9% over 72 weeks alongside lifestyle changes. The STEP-1 trial showed Wegovy at 2.4 mg achieved approximately clinically studied weight loss over 68 weeks. However, individual results vary significantly — these are trial averages, not assured outcomes.
Both medications require a prescription and clinical assessment from a UK-licensed prescriber. Your suitability depends on your BMI, weight-related health conditions, medical history, and current medications. Your prescriber will consider factors like your tolerance to nausea and gastroparesis risk. Neither medication is suitable during pregnancy, and both require barrier contraception if you take oral contraceptives. Try our free GLP-1 weight loss calculator to explore projected outcomes, and use the BMI calculator to check your starting point.
- 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.
What does "clicks" mean on a Mounjaro pen?
Mounjaro's KwikPen has numbered clicks that deliver specific doses. Your prescriber tells you the number of clicks to use each week — for example, "click to 2" for the 2.5 mg starting dose. Each click setting dispenses a precise amount. This differs from Wegovy, which uses pre-filled pens at fixed doses.
Is Mounjaro more effective than Wegovy?
Clinical trial data shows Mounjaro achieved slightly higher average weight loss (15–21%) compared to Wegovy (14.9%) in their respective trials. However, direct comparisons are limited, and individual results vary considerably. Both are effective for weight management when used alongside lifestyle changes. Your prescriber will recommend the most suitable option for you.
Which injection is easier to use — Mounjaro or Wegovy?
Both are once-weekly injections designed for ease of use. Mounjaro's KwikPen with click dosing may feel more flexible, whilst Wegovy's pre-filled pens are simpler in that you don't adjust a dose dial. Both require subcutaneous injection into the stomach, thigh, or upper arm. Your comfort with either system may vary.
Can I switch from Wegovy to Mounjaro in the UK?
Switching between medications is possible but must be managed by your prescriber. There's no official NHS conversion chart, though approximate equivalences exist (for example, Wegovy 1.7 mg is roughly equivalent to Mounjaro 10 mg). Your prescriber will advise on timing and how to transition safely.
How do I access Mounjaro or Wegovy on the NHS?
Both medications are available through NHS specialist weight management services (Tier 3), but availability varies significantly by region and there are often long waiting lists. Private access is available through GPhC-registered online pharmacies following a clinical assessment. Your GP can discuss both options with you.
Ready to take control of your weight loss journey?
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