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 First Order Discount vs Wegovy — What You Need to Know
When researching Mounjaro first order discounts and weight management injections in the UK, it's worth understanding how Mounjaro compares to Wegovy. Both are prescription-only GLP-1-based medications approved for weight management, but they work differently and may suit different people. This guide compares their mechanisms, clinical trial data, and what to expect when starting either medication so you can make an informed decision 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.
Clinical Trial Data and Weight Loss Mechanisms
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways that regulate appetite and blood sugar. In the SURMOUNT-1 clinical trial, participants taking Mounjaro 15 mg achieved an average weight loss of approximately 20.9% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1-only receptor agonist, activating a single appetite-regulating pathway. In the STEP-1 clinical trial, participants achieved an average weight loss of approximately 14.9% of their body weight over 68 weeks under similar lifestyle conditions.
These averages come from clinical trials — individual results vary significantly based on dose, adherence, lifestyle changes, and personal metabolism. Both medications require prescription and a clinical assessment to determine suitability. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, though actual results will differ from person to person.
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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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Eligibility, Dosing, and Your Prescriber's Role
Both Mounjaro and Wegovy are prescribed to UK adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Lower BMI thresholds may apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower weights.
Mounjaro starts at 2.5 mg and escalates to a maximum of 15 mg weekly, while Wegovy starts at 0.25 mg and escalates to 2.4 mg weekly. Neither medication has a assured "first order discount" — pricing varies by provider and dose. Your prescriber will assess which medication suits your individual health profile, medical history, and any existing medications. The choice depends on clinical suitability, not price alone.
- 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 there an official first order discount for Mounjaro in the UK?
There is no official NHS-wide first order discount for Mounjaro. Private providers may offer varying pricing structures, and some may include promotional discounts for first orders. Costs typically range from £129–£320 per month depending on dose and provider. Always compare total cost across doses, not just the first injection. Your prescriber will advise on access routes and pricing.
What is the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that activates two appetite-regulating pathways, whilst Wegovy (semaglutide) activates only the GLP-1 pathway. This dual mechanism may contribute to Mounjaro's higher average weight loss in clinical trials (approximately 20.9% vs 14.9%), though individual results vary significantly and clinical suitability depends on personal health factors.
Can I switch from Wegovy to Mounjaro or vice versa?
Yes, switching between medications is possible, but it must be managed by your prescriber. There is no official conversion chart between the two — approximate equivalences exist (e.g., Mounjaro 10 mg roughly equivalent to Wegovy 1.7 mg), but any switch requires clinical assessment. Your prescriber will advise on timing and dose adjustments based on your individual response.
Will my GP prescribe Mounjaro or Wegovy on the NHS?
Standard GP prescription of Mounjaro or Wegovy is not common on the NHS. Access is typically through NHS tier 3 specialist weight management services following referral, though availability varies significantly by region and waiting lists can be lengthy. Private online prescribing via licensed UK prescribers is an alternative route that does not require NHS referral.
How do I know which medication is right for me?
Only a licensed prescriber can assess your eligibility and suitability for either medication based on your BMI, health conditions, medical history, current medications, and personal circumstances. Both require a clinical assessment before prescription. Check your BMI using our free BMI calculator, then discuss your options with your GP or a licensed online prescriber to determine the best option for your health profile.
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