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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Wegovy vs Mounjaro: Dosage Chart and NHS Prescribing Guide
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections licensed in the UK, but they have different dosage schedules and mechanisms. This guide compares both medications side-by-side, explains NHS eligibility criteria, and outlines what the clinical trial data actually shows. Whether you're exploring NHS specialist tier 3 services or private prescribing, understanding the difference between these two injection schedules will help you have an informed conversation with your GP or 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.
How Wegovy and Mounjaro Dosages Compare
Wegovy (semaglutide) is a GLP-1 receptor agonist that escalates over five weeks to reach the 2.4 mg maintenance dose. Starting at 0.25 mg weekly, it increases to 0.5 mg, 1 mg, 1.7 mg, then 2.4 mg. Each dose is held for 4 weeks before escalation.
Mounjaro (tirzepatide) uses a different titration pathway, starting at 2.5 mg and escalating through 5 mg, 7.5 mg, 10 mg, 12.5 mg, to a maximum of 15 mg weekly. Mounjaro is a dual GIP and GLP-1 agonist, meaning it activates two hormone pathways rather than one.
- Wegovy maximum: 2.4 mg once weekly
- Mounjaro maximum: 15 mg once weekly
- Both: Require minimum 4 weeks at each dose before escalation
- Clinical trial data: STEP-1 (Wegovy) showed ~15% average weight loss; SURMOUNT-1 (Mounjaro) showed ~21% average weight loss, though individual results vary significantly
Neither medication is suitable for children under 18, those who are pregnant or breastfeeding, or people with severe gastroparesis or pancreatitis history. A prescriber will assess your individual eligibility before prescribing either medication.
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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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NHS Access, Eligibility, and the Private Route in the UK
NHS access to both Wegovy and Mounjaro is through specialist tier 3 weight management services, typically after referral from your GP. NICE has approved both tirzepatide (Mounjaro) and semaglutide (Wegovy) for NHS use, but availability varies significantly by region and ICB (Integrated Care Board). Waiting lists can stretch many months in some areas.
Private access in the UK is faster—both medications are available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Private costs range from approximately £129–£320 monthly depending on dose.
Eligibility criteria (both NHS and private): BMI of 30 or above, or 27–29.9 with weight-related health conditions including type 2 diabetes, prediabetes, hypertension, dyslipidaemia, sleep apnoea, or cardiovascular disease history. South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds (27.5+).
Use our free GLP-1 weight loss calculator to estimate potential weight loss at different doses, and try the BMI calculator to check if you may meet eligibility criteria.
- 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.
Which medication causes more weight loss, Wegovy or Mounjaro?
Based on clinical trials, Mounjaro (tirzepatide) showed slightly higher average weight loss (~21% body weight) compared to Wegovy (~15% body weight). However, individual results vary significantly. Some people respond better to one medication than the other. Your prescriber will help determine which is more appropriate for you.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications is possible but typically requires specialist assessment. There is no official conversion chart between Wegovy and Mounjaro doses. An approximate equivalence exists (Wegovy 2.4 mg ≈ Mounjaro 10–15 mg), but any switch must be managed by your prescriber or specialist service. NHS tier 3 services vary in their switching protocols.
How long does it take to reach the maximum dose of each medication?
Wegovy takes 16 weeks to reach maximum (0.25 mg → 2.4 mg with 4-week intervals). Mounjaro takes approximately 20 weeks to reach 15 mg maximum. Both require 4 weeks at each dose step before escalation. Escalation can be paused if side effects occur.
Are Wegovy and Mounjaro available on the NHS in my area?
Availability varies by region. Ask your GP for a referral to your local tier 3 weight management service—they will advise on access in your area. Private access through online prescribing is available nationwide if NHS waiting times are lengthy or services are unavailable locally.
Do I need to continue Wegovy or Mounjaro indefinitely?
These are not permanent solutions. Guidance suggests treatment continues whilst benefiting and tolerating the medication. When stopped, weight regain can occur, which is why lifestyle changes (diet and exercise) are crucial alongside medication. Your prescriber will discuss duration and monitoring with you.
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.