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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Wegovy vs Mounjaro for Diabetes — What's the Difference?
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight loss medications available in the UK that may support weight management in adults with type 2 diabetes. However, they work differently and have different trial evidence. Understanding how they compare can help you and your GP or prescriber make an informed decision about which might be suitable for you. Both require a clinical assessment before prescription, and results vary between individuals.
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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 — Key Differences
Wegovy (semaglutide) is a GLP-1 receptor agonist, meaning it activates a single natural hormone pathway (GLP-1) that helps regulate appetite and blood sugar control. This single mechanism has been well-researched for over a decade in type 2 diabetes treatment.
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, activating two hormone pathways simultaneously. This dual mechanism is newer—tirzepatide was approved for weight management more recently than semaglutide. Clinical trial data from the SURMOUNT-1 study showed Mounjaro participants lost an average of approximately 20.9% body weight at the maximum 15 mg dose, whilst the STEP-1 trial showed Wegovy participants lost approximately 14.9% body weight at the maximum 2.4 mg dose. Both medications require a reduced-calorie diet and increased physical activity to be effective. Individual results vary significantly.
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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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Choosing Between Them — What Your Prescriber Will Consider
Neither medication is universally "better"—suitability depends on your individual health profile, other medications you take, and how you respond to treatment. Wegovy (semaglutide) is an established GLP-1 receptor agonist with longer-term safety data, whilst Mounjaro's dual mechanism may offer additional benefits for some people, though it's a newer option. Your GP or prescriber will assess factors including your diabetes status, other health conditions, current medications, and personal preference. Access to both medications in the UK is through NHS specialist tier 3 weight management services or private online prescribing following a clinical assessment. Try our free GLP-1 weight loss calculator above to explore potential outcomes at different doses of either medication.
- 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.
Can I take Wegovy if I have type 2 diabetes?
Yes. Wegovy (semaglutide) is a GLP-1 receptor agonist that helps regulate blood sugar, making it suitable for people with type 2 diabetes. Many people use it specifically for diabetes management at lower doses (as Ozempic), whilst the higher-dose Wegovy formulation is licensed for weight management. Your GP or prescriber will assess your suitability based on your individual health profile and current medications.
What's the main difference between Wegovy and Mounjaro?
Wegovy activates one hormone pathway (GLP-1), whilst Mounjaro activates two pathways (GIP and GLP-1). This dual mechanism may offer additional effects, though clinical trial results show both support meaningful weight loss. Wegovy has longer safety data; Mounjaro is newer. Both are prescription-only and require clinical assessment. Individual results vary.
Which causes fewer side effects — Wegovy or Mounjaro?
Both have similar common side effects including nausea, diarrhoea, and constipation—especially during dose escalation. Individual tolerance varies significantly. Your prescriber will monitor you and adjust doses or support symptom management. Neither medication is inherently "easier" for everyone. Personal response matters more than the medication choice.
How do I access Wegovy or Mounjaro on the NHS in the UK?
Both are available through NHS specialist tier 3 weight management services following referral from your GP. However, NHS availability varies significantly by region. Waiting lists can be lengthy. Private access is available through GPhC-registered online pharmacies following a clinical assessment by a UK-licensed prescriber, though this involves private costs.
Do I need to use the NHS weight loss calculator to compare Wegovy and Mounjaro?
Our free GLP-1 weight loss calculator on this page allows you to explore projected weight loss outcomes at different doses of either medication based on clinical trial data. This can help visualise potential results, though individual outcomes vary. Always discuss trial data and realistic expectations with your prescriber before starting any medication.
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.