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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Why Is Mounjaro Going Up In Price On The NHS?
Mounjaro (tirzepatide) pricing on the NHS has become a significant consideration for adults seeking weight management treatment. Unlike some medications, NHS availability and cost vary considerably by region, and pricing pressures affect access across the UK. This guide explains the pricing landscape for Mounjaro, how it compares to Wegovy (semaglutide), and what options may be available to you. Use our free GLP-1 weight loss calculator to explore potential outcomes with either medication, and consult your GP about eligibility and access in your area.
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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.
Mounjaro vs Wegovy: Mechanism, Dosing, and Trial Data
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both GLP-1 medications licensed for weight management in the UK, but they work differently and have different cost profiles. Mounjaro is a dual GIP and GLP-1 receptor agonist — it activates two hormone pathways — whereas Wegovy is a GLP-1-only agonist. This dual mechanism may explain why Mounjaro showed slightly higher average weight loss in clinical trials (approximately 15–21% body weight with Mounjaro SURMOUNT trial vs 15% with Wegovy STEP trial), though individual results vary significantly.
Mounjaro dosing starts at 2.5 mg and escalates through dose titration up to a maximum of 15 mg once weekly. Wegovy starts at 0.25 mg and escalates to 2.4 mg once weekly. Both require a clinical assessment before prescription and both work alongside reduced-calorie diet and increased physical activity. NHS pricing for both medications fluctuates based on national procurement agreements, which is why costs and availability vary by region and time.
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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 Availability, Private Access, and Which Medication May Suit You
Access to both Mounjaro and Wegovy through the NHS is limited and typically requires referral to a specialist tier 3 or tier 4 weight management service. Waiting lists can be very long in many regions, and availability depends on your local Integrated Care Board (ICB) budget and decisions. NICE has approved both tirzepatide and semaglutide for NHS use, but provision remains patchy across the UK.
Privately, both medications are available through online clinical assessment with UK-licensed prescribers and dispensed by GPhC-registered pharmacies. A prescriber will assess your eligibility based on BMI (30 or above, or 27–29.9 with weight-related health conditions) and any contraindications. Neither medication is suitable if you are pregnant, planning pregnancy, or have a personal or family history of medullary thyroid cancer. Your GP or prescriber can advise which is more appropriate for your individual health profile.
- 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.
Why is Mounjaro more expensive than Wegovy on the NHS?
Mounjaro pricing reflects its dual GIP+GLP-1 mechanism and manufacturing costs. Wegovy (single GLP-1 agonist) may have different procurement pricing. However, NHS pricing varies by region and time — there is no fixed national price, and costs are negotiated between NHS England and manufacturers based on clinical guidelines and budget availability.
Which medication is more effective for weight loss — Mounjaro or Wegovy?
Clinical trial data shows Mounjaro (SURMOUNT) produced slightly higher average weight loss (15–21%) than Wegovy (STEP trial, ~15%). However, individual results vary considerably, and effectiveness depends on adherence, lifestyle changes, and personal response. Your prescriber will assess which is more suitable based on your health profile and eligibility.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between GLP-1 medications on the NHS is possible but requires prescriber approval and typically involves NHS specialist services. The approximate equivalent doses are: Wegovy 0.5 mg ≈ Mounjaro 5 mg, Wegovy 1.7 mg ≈ Mounjaro 10 mg, Wegovy 2.4 mg ≈ Mounjaro 15 mg. Any switch must be managed by your healthcare team.
How can I check if I am eligible for weight loss medication on the NHS?
You are typically eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Use our free BMI calculator to check your BMI, then discuss NHS referral options with your GP. South Asian, Chinese, Black African, and Caribbean adults may have lower thresholds — ask your GP for specific guidance.
What are the main side effects I should expect with Mounjaro or Wegovy?
Both medications commonly cause nausea, diarrhoea, constipation, and stomach pain — typically mild and temporary during dose titration. Rare serious side effects include pancreatitis and gallbladder problems. Side effects tend to improve as your body adjusts. Your prescriber will monitor you and discuss any concerns. Always report severe symptoms to your GP immediately.
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.