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 and Mounjaro Dose Comparison for UK Adults
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections licensed in the UK, but they differ significantly in their dosing schedules and mechanisms. Wegovy is a single GLP-1 receptor agonist, whilst Mounjaro is a dual GIP and GLP-1 agonist — this difference is reflected in their dose ranges and titration protocols. Understanding how these medications work and what NHS and private access looks like in the UK is essential if you're considering either option for weight management support.
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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 Doses Compare
Wegovy (semaglutide) starts at 0.25 mg once weekly and titrates upward every 4 weeks, with a maximum dose of 2.4 mg once weekly. Most patients reach maintenance at the 2.4 mg dose, which is the standard effective dose used in the STEP clinical trials.
Mounjaro (tirzepatide) begins at 2.5 mg once weekly and escalates to a maximum of 15 mg once weekly — significantly higher than Wegovy's maximum dose. This reflects tirzepatide's dual-action mechanism; lower doses may achieve effects similar to higher Wegovy doses due to the additional GIP receptor pathway.
- Wegovy maximum: 2.4 mg once weekly
- Mounjaro maximum: 15 mg once weekly
- Approximate equivalence: Mounjaro 5 mg ≈ Wegovy 0.5 mg; Mounjaro 10 mg ≈ Wegovy 1.7 mg; Mounjaro 15 mg ≈ Wegovy 2.4 mg (these are approximate only — no official NHS conversion exists)
Clinical trial data shows both medications produce meaningful weight loss when used alongside reduced-calorie diet and physical activity, though individual results vary considerably. Your prescriber will determine the appropriate starting and maintenance dose based on your tolerability and response.
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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 and Prescribing Context in the UK
Both Wegovy and Mounjaro are available through NHS specialist tier 3 weight management services and via private prescription from UK-licensed online prescribers. NHS access requires referral from your GP to a specialist weight management service, which may involve a waiting list — availability varies significantly by region and Integrated Care Board (ICB).
The NICE guidance on weight management supports both medications for eligible adults. An NHS prescriber will assess your BMI (30 kg/m² or above, or 27 kg/m² with weight-related health conditions), medical history, and contraindications before issuing a prescription.
Use our free GLP-1 weight loss calculator to explore potential weight loss outcomes at different doses, and our BMI calculator to check your starting point and track how your BMI changes during treatment.
- 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.
What's the main difference between Wegovy and Mounjaro doses?
Wegovy is a GLP-1 only medication with a maximum dose of 2.4 mg weekly. Mounjaro is a dual GIP/GLP-1 medication with a maximum dose of 15 mg weekly. Because tirzepatide (Mounjaro) works on two pathways, lower absolute doses may produce similar effects to higher Wegovy doses. Direct dose-for-dose comparison is not straightforward — your prescriber will recommend the most appropriate medication and dose for you.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications is possible but must be managed by your NHS specialist prescriber or private prescriber. There's no official NHS protocol for switching — your prescriber will assess whether a change is clinically appropriate based on your response, side effects, and health goals. Any switch requires a new clinical assessment and prescription.
What's the starting dose for Wegovy in the UK?
Wegovy starts at 0.25 mg once weekly. Your dose increases by 0.25 mg each week for the first month, then moves to 0.5 mg for weeks 5–8, continuing to escalate every 4 weeks to a maximum of 2.4 mg. This gradual titration helps minimise side effects and allows your body to adjust.
What's the starting dose for Mounjaro in the UK?
Mounjaro starts at 2.5 mg once weekly. After a minimum of 4 weeks, the dose can be increased to 5 mg, then 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg maximum. Your prescriber will titrate based on your tolerability and weight loss response — you don't necessarily need to reach the maximum dose.
How long does it take to reach the maximum dose on both medications?
Wegovy reaches maximum dose (2.4 mg) by week 16. Mounjaro can reach maximum dose (15 mg) by week 20 or later, depending on tolerability. Most patients reach an effective maintenance dose well before the maximum — individual needs vary, so your prescriber will determine the optimal dose for you.
Ready to take control of your weight loss journey?
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