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
Cheapest Mounjaro Pen vs Wegovy — Which Costs Less?
If you're considering GLP-1 weight loss treatment in the UK, cost is understandably a factor. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only injectable medications, but they differ in mechanism, dosing, and pricing. This guide compares the two medications factually so you can understand what to expect when discussing options with your prescriber. Remember, the cheapest option isn't necessarily the right choice for you — suitability depends on your individual health profile, not cost alone.
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 Compare — Clinical Differences
Mechanism: Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. Wegovy (semaglutide) activates GLP-1 only. This difference affects how each medication works in your body.
Dosing and titration: Mounjaro starts at 2.5 mg and increases to a maximum of 15 mg weekly over 20 weeks. Wegovy starts at 0.25 mg and reaches 2.4 mg maximum over 16 weeks. Mounjaro's higher doses may relate to its dual mechanism — each medication works differently, so direct dose comparison is not meaningful.
Clinical trial results: The SURMOUNT-1 trial showed Mounjaro participants lost an average of 20.9% body weight at 15 mg. The STEP-1 trial showed Wegovy participants lost approximately 14.9% body weight at 2.4 mg. However, individual results vary significantly — these are population averages, not assures. Your prescriber will assess which medication suits your health profile best.
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 Comparison and How to Access Both Medications
Private pricing for both medications ranges approximately £129–£320 per month depending on dose. Mounjaro's larger maximum dose (15 mg) may cost slightly more at the highest tier, but entry-level costs are comparable. Both require a prescription from a UK-licensed prescriber following a clinical assessment — pricing varies by provider.
NHS access: Both Mounjaro and Wegovy can be accessed through NHS specialist weight management services, though NICE approval means both are available in principle. In practice, NHS availability and waiting times vary significantly by region (ICB). Many people pursue private prescribing for faster access. Your prescriber will discuss which medication is clinically appropriate for you — cost alone should not drive the decision, as effectiveness and side effect profile matter more for your individual health.
- 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 pricing is generally comparable — both range £129–£320/month depending on dose. Mounjaro's higher maximum dose (15 mg vs 2.4 mg) may cost slightly more at the highest tier, but starter doses are similar. NHS pricing is free but access varies by region. Your prescriber will recommend based on clinical suitability, not cost.
Which medication causes more weight loss — Mounjaro or Wegovy?
Clinical trials showed Mounjaro achieved approximately 20.9% average weight loss and Wegovy 14.9%, but individual results vary significantly. The difference may relate to Mounjaro's dual mechanism (GIP+GLP-1 vs GLP-1 only). Your prescriber will discuss expected outcomes based on your health profile.
Can I switch from Wegovy to Mounjaro to save money?
Any switch between medications must be managed by your prescriber — cost is not a clinical reason to switch. If you're on Wegovy and your prescriber believes Mounjaro would be more suitable for your health, that's a prescriber decision based on efficacy and side effects, not savings.
What's the difference between Mounjaro and tirzepatide?
Mounjaro is the brand name for tirzepatide. They're the same medication — Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist available as a once-weekly injectable pen. Tirzepatide is the active ingredient; Mounjaro is the branded delivery.
How do I access the cheapest option on the NHS?
Both Mounjaro and Wegovy are free on the NHS, but availability depends on your regional ICB and specialist weight management services. Ask your GP for a referral to your local tier 3 weight management service. Waiting times and medication availability vary significantly by region — private prescribing may be faster if you're willing to pay.
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.