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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1mg Wegovy Compared to Mounjaro: What's the Difference?
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections licensed in the UK, but they work differently. At 1mg Wegovy, you're mid-way through the dose escalation, while Mounjaro's 1mg equivalent isn't a direct comparison due to different mechanisms. This guide compares the two medications side-by-side so you understand how they differ in action, trial results, and eligibility. Both require clinical assessment from a prescriber before use.
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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 Wegovy and Mounjaro Work Differently
Wegovy (semaglutide) is a GLP-1 receptor agonist — it activates a single hormone pathway to reduce appetite and increase feelings of fullness. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways simultaneously. This dual mechanism is what makes Mounjaro different. In clinical trials, the STEP-1 trial showed Wegovy achieved an average weight loss of approximately 14.9% at the 2.4mg maximum dose over 68 weeks alongside a reduced-calorie diet and increased physical activity. The SURMOUNT-1 trial showed Mounjaro at 15mg achieved approximately 20.9% average weight loss over 72 weeks under similar conditions. However, individual results vary significantly. The 1mg dose in Wegovy is part of the escalation pathway (typically weeks 9–12), while Mounjaro's escalation follows a different schedule. Both are once-weekly injections delivered via pre-filled pens.
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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.
Eligibility, Doses, and Prescriber Decisions
Both medications follow the same UK eligibility criteria: BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. South Asian, Chinese, Black African, or Black Caribbean adults may qualify at lower BMI thresholds (from 27.5). Wegovy escalates from 0.25mg to a maximum of 2.4mg, while Mounjaro escalates from 2.5mg to 15mg — different dose ranges entirely. You'll need a clinical assessment from a prescriber to determine which medication, if either, suits your individual health profile. Available through NHS specialist weight management services or private prescribing following an online consultation. Try our free GLP-1 weight loss calculator to explore potential 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.
Is 1mg Wegovy equivalent to any Mounjaro dose?
Not directly. Approximate equivalences are 1mg Wegovy ≈ 7.5mg Mounjaro, but these are rough guidelines only. Both medications have different mechanisms and dose escalation schedules. Any switch between them must be managed by your prescriber.
Which has fewer side effects, Wegovy or Mounjaro?
Side effect profiles are similar — nausea, diarrhoea, constipation, and vomiting are common with both. Individual tolerance varies. Your prescriber will help determine which is most suitable based on your medical history.
Can I switch from Wegovy 1mg to Mounjaro mid-treatment?
Potentially, yes, but only under prescriber guidance. Switching medications requires careful assessment and planning. Never change without consulting your prescriber.
How long does it take to see weight loss results on Wegovy or Mounjaro?
Clinical trials showed measurable weight loss typically begins within 4–8 weeks, but varies by individual. Both are most effective alongside a reduced-calorie diet and increased physical activity.
Are Wegovy and Mounjaro available on the NHS in the UK?
Both are NHS-eligible but access is through tier 3 specialist weight management services. Availability varies by region and waiting times can be long. Private prescribing is available through online clinical assessments without NHS referral.
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.