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
Is Mounjaro The Same As Wegovy?
No, Mounjaro and Wegovy are not the same, although both are prescription-only weight loss injections used in the UK. The key difference is their active ingredients and how they work. Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist, while Wegovy contains semaglutide, a GLP-1 receptor agonist only. Both are licensed for weight management in UK adults, but they differ in dosing, cost, and availability. Understanding these differences helps you and your prescriber decide which option might be more suitable for 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 Mounjaro And Wegovy Differ — And UK Cost Context
Active ingredient: Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates GLP-1 only. This dual mechanism is why Mounjaro may produce slightly different results for some people.
Dosing and strength: Mounjaro starts at 2.5 mg and escalates to a maximum of 15 mg once weekly. Wegovy starts at 0.25 mg and escalates to a maximum of 2.4 mg once weekly. Despite the higher numerical dose, these are not directly comparable — the medications work differently.
UK private prescription costs: Both medications are available through private online prescription pathways in the UK. Mounjaro typically costs £150–£280 per month depending on dose. Wegovy typically costs £129–£320 per month depending on dose. Prices vary between providers and occasionally change. Neither cost includes the prescription consultation fee, which is usually £30–£100.
Weight loss outcomes: Clinical trials show Mounjaro users lost an average of 15–21% body weight, while Wegovy users lost approximately 15% body weight on average. However, individual results vary significantly, and both medications work best alongside lifestyle changes.
Clinically BackedWeight Loss
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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.
NHS Access Vs Private Route — How To Get A Prescription
NHS route: Both Mounjaro and Wegovy are available through NHS specialist weight management services (tier 3), but only if referred by your GP and assessed as eligible. NICE has approved both medications for NHS use. Access is free but involves waiting lists that can extend many months or years in some regions. Eligibility requires a BMI of 30 or above, or 27 or above with weight-related health conditions. Use our free BMI calculator above to check where you stand.
Private route: Both medications are available through GPhC-registered online prescription services without NHS referral. You complete an online health questionnaire, have a video consultation with a UK-licensed prescriber, and receive a prescription if clinically appropriate. The process typically takes 1–2 days. You pay for the prescription consultation and the medication. This route avoids NHS waiting lists but costs more upfront.
- 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 the same as the tirzepatide in Mounjaro KwikPen?
Yes. Mounjaro is the brand name; tirzepatide is the active ingredient. The KwikPen is simply the injection device. All Mounjaro pens contain tirzepatide at the same doses — the KwikPen is just how it's delivered.
What's the main difference between Mounjaro and Wegovy in the UK?
Mounjaro (tirzepatide) activates two hormone pathways — GIP and GLP-1. Wegovy (semaglutide) activates GLP-1 only. This dual mechanism may affect how they work and which medication suits different people. Your prescriber can discuss which is more appropriate for you.
Can I switch from Mounjaro to Wegovy or vice versa?
Switching between medications is possible but must be managed by your prescriber. There is no official conversion chart — your prescriber will assess the timing and dosing for any switch. You cannot simply stop one and start the other without guidance.
How do I check if I'm eligible for either Mounjaro or Wegovy on the NHS?
You need a BMI of 30 or above, or 27 or above with weight-related conditions like type 2 diabetes, high blood pressure, or heart disease. Check your BMI using our free BMI calculator, then speak to your GP about referral to a specialist weight management service.
What's included in the monthly cost of Mounjaro or Wegovy in the UK?
The monthly cost covers the medication pens only. It does not include the initial prescription consultation fee (usually £30–£100) or follow-up consultations. Some providers offer subscription models that bundle support, but this varies. Always check what's included when comparing providers.
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.