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
Free tracker included with every download this week
Mounjaro vs Wegovy: Cost and Value in the UK
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only weight loss injections available in the UK, but they differ in cost, mechanism, and expected outcomes. Understanding the differences helps you and your prescriber decide which might offer better value for your individual health situation. Both require a clinical assessment before prescription, and real-world costs vary depending on where you access treatment—NHS specialist services or private online providers. This guide compares the two honestly so you can make an informed decision.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 Differ: Mechanism and Trial Results
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways for appetite and blood sugar control. Clinical trials (SURMOUNT-1) showed average weight loss of approximately 15–21% of body weight over 72 weeks, depending on dose. The highest dose (15 mg) achieved roughly clinically studied weight loss alongside diet and exercise changes.
Wegovy (semaglutide) is a single GLP-1 receptor agonist activating one hormone pathway. The STEP-1 clinical trial showed average weight loss of approximately 14.9% of body weight at the maximum dose (2.4 mg) over 68 weeks. Both use a dose titration schedule—you start low and gradually increase every 4 weeks.
- Mounjaro: 2.5 mg up to 15 mg per week
- Wegovy: 0.25 mg up to 2.4 mg per week
Individual results vary significantly, and weight loss depends on adherence to reduced-calorie diet and physical activity alongside medication.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
UK Cost, Availability, and Which Suits You Best
Private UK bundle costs vary by provider and dose: Mounjaro typically ranges from £129–£320 per month depending on strength, while Wegovy costs similarly. Both require a prescription from a UK-licensed prescriber following an online clinical assessment. NHS access is through specialist weight management services (tier 3), though waiting times and regional availability vary widely—access is not assured.
Your prescriber will recommend based on your health history, existing medications (Mounjaro may affect oral contraceptive absorption), and medical conditions. Neither medication is "cheaper" intrinsically—value depends on which works better for your body and health profile. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and our BMI calculator to check your eligibility baseline.
- 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 Mounjaro cheaper than Wegovy in the UK?
Private UK prices are similar—both range £129–£320 monthly depending on dose. Mounjaro's higher maximum dose (15 mg vs Wegovy's 2.4 mg) means maximum-strength Mounjaro may cost more per month. NHS access depends on your region and specialist service availability, not the medication itself.
Which caused more weight loss in clinical trials?
In head-to-head trials, Mounjaro (SURMOUNT) showed slightly higher average weight loss (up to 20.9%) than Wegovy (STEP, 14.9%). However, individual results vary widely. A prescriber will recommend based on your specific health situation, not trial averages.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching between medications requires prescriber guidance and is not a simple dose swap. An approximate equivalent might be Wegovy 0.5 mg ≈ Mounjaro 5 mg, but this varies by individual response. Always discuss any switch with your prescriber.
What's the difference between a kwikpen and standard injection?
Mounjaro comes as a pre-filled KwikPen (4 doses per pen), while Wegovy uses a pre-filled auto-injection pen. Both are once-weekly injections. KwikPen is simply Eli Lilly's delivery device name—it works the same way as other pre-filled pens.
Do I need a prescription even for private weight loss injections?
Yes. Both Mounjaro and Wegovy are prescription-only medicines in the UK. You must have a consultation with a UK-licensed prescriber who will assess your eligibility before issuing a prescription to a GPhC-registered pharmacy.
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.