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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How Does 1mg Wegovy Compare to Mounjaro?
At 1mg, Wegovy (semaglutide) and Mounjaro (tirzepatide) represent different stages of their respective dose schedules and use different mechanisms of action. Wegovy's 1mg dose is a mid-range escalation dose in the STEP trial, while an equivalent Mounjaro dose would be around 5mg based on clinical potency. Both are prescription-only GLP-1 and GIP/GLP-1 receptor agonists licensed in the UK for weight management in adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Understanding how these doses compare can help you and your prescriber decide which medication might suit your situation.
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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 the Doses Compare in Practice
Wegovy at 1mg sits roughly four weeks into the standard escalation schedule (weeks 9–12), while Mounjaro's approximate equivalent potency would be around 5mg (weeks 5–8+). This is an important distinction: they are not direct dose-for-dose equivalents. Wegovy uses a single GLP-1 mechanism, whereas Mounjaro activates both GIP and GLP-1 pathways, making direct numerical comparisons misleading.
In the STEP-1 clinical trial, participants on Wegovy 1mg achieved modest weight loss; by the final 2.4mg dose, average weight loss was approximately 14.9% of body weight over 68 weeks alongside a reduced-calorie diet and increased physical activity. Mounjaro users on 5mg in SURMOUNT trials showed average weight loss of approximately 15% body weight. Individual results vary significantly based on adherence, lifestyle changes, and personal metabolism.
Both require once-weekly injections and are available through NHS specialist weight management services or private prescribing in the UK.
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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.
Mechanism Differences and What They Mean for You
Wegovy activates GLP-1 receptors only, signalling fullness and reducing appetite through a single hormone pathway. Mounjaro activates both GIP and GLP-1 pathways simultaneously, which may explain why some users report stronger appetite suppression. Neither is superior — effectiveness depends on your individual response.
Both medications slow gastric emptying (how quickly food leaves your stomach) and help regulate blood sugar. Common side effects overlap: nausea, diarrhoea, constipation, and vomiting, typically most pronounced during dose escalation. Your GP or prescriber will assess which suits you based on your health history, any weight-related conditions (like type 2 diabetes or high blood pressure), and previous medication experiences. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses.
- 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 5mg Mounjaro?
Approximately, yes. Based on clinical trial data and prescribing practice, 1mg Wegovy and 5mg Mounjaro show broadly similar weight loss outcomes. However, they're not direct equivalents because Mounjaro uses a dual GIP/GLP-1 mechanism whilst Wegovy uses GLP-1 only. Any switch between medications must be managed by your prescriber, never self-managed.
Which causes fewer side effects, Wegovy or Mounjaro?
Side effect profiles are very similar — both commonly cause nausea, diarrhoea, and constipation. Individual tolerance varies significantly. Some users report stronger appetite suppression on Mounjaro; others do equally well on Wegovy. Your prescriber will discuss this during your clinical assessment.
Can I switch from 1mg Wegovy to Mounjaro?
Yes, but only under prescriber guidance. There is no official conversion chart, but approximate equivalence suggests 1mg Wegovy ≈ 5mg Mounjaro. Your prescriber may restart escalation or adjust timing based on your response to Wegovy. Never switch medications without clinical supervision.
Is Wegovy or Mounjaro available on the NHS in the UK?
Both are available through NHS tier 3 specialist weight management services, though availability varies significantly by region and waiting lists can be long. Both are also available privately through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes (up to 2mg dose) and is not approved for weight management in the UK. Wegovy is the licensed weight management version (up to 2.4mg). Using Ozempic for weight loss is off-label and not recommended in UK practice.
Ready to take control of your weight loss journey?
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