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 Dosing: What's the Difference?
Wegovy and Mounjaro are both UK-licensed weight loss injections with different dosing schedules and mechanisms. Wegovy (semaglutide) is a GLP-1 receptor agonist, while Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist — this difference affects how they're dosed and escalated. Understanding the dosing timeline for each can help you understand what to expect if prescribed either medication. Both are prescription-only and require clinical assessment before being prescribed by your GP or private prescriber.
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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.
Dosing Schedule Comparison: Wegovy vs Mounjaro
Wegovy starts at 0.25 mg and escalates over 16 weeks to a maximum of 2.4 mg once weekly. The starting dose is the smallest, increasing every 4 weeks until reaching the maintenance dose. Mounjaro begins at 2.5 mg and escalates over 20 weeks to a maximum of 15 mg once weekly — both are given as once-weekly injections in a KwikPen device.
- Wegovy: 0.25 mg (weeks 1–4), 0.5 mg (weeks 5–8), 1 mg (weeks 9–12), 1.7 mg (weeks 13–16), 2.4 mg (week 17+)
- Mounjaro: 2.5 mg (weeks 1–4), 5 mg (weeks 5–8), 7.5 mg (weeks 9–12), 10 mg (weeks 13–16), 12.5 mg (weeks 17–20), 15 mg (week 21+)
Each dose is held for a minimum of 4 weeks before escalation. Clinical trials (STEP for Wegovy, SURMOUNT for Mounjaro) used these dose titration schedules to determine safety and weight loss outcomes.
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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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Which Dosing Schedule Is Right for You?
The choice between Wegovy and Mounjaro dosing is not about which schedule is "better" — it's about which medication your prescriber assesses as suitable for your individual health, medical history, and weight loss goals. Wegovy's lower starting dose may suit some people; Mounjaro's dual mechanism and different escalation pattern may be appropriate for others. Both require a clinical assessment from your GP or a licensed prescriber, who will determine eligibility based on your BMI and weight-related health conditions. Use our free GLP-1 weight loss calculator to explore potential weight loss outcomes at different doses, and discuss the results with your prescriber during your consultation.
- 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 dosing?
Wegovy starts at 0.25 mg and escalates to 2.4 mg maximum; Mounjaro starts at 2.5 mg and escalates to 15 mg. Mounjaro's higher absolute doses reflect its dual GIP+GLP-1 mechanism versus Wegovy's single GLP-1 action. Both use 4-week dose intervals, but Mounjaro's escalation timeline is longer overall.
How long does it take to reach the maximum dose on each medication?
Wegovy reaches maximum (2.4 mg) in 16 weeks; Mounjaro reaches maximum (15 mg) in 20 weeks. Both require staying on each dose for at least 4 weeks before increasing, so the full titration is a structured process. Some people may stabilise on a lower dose and not escalate further.
Can you switch from Wegovy to Mounjaro dosing mid-treatment?
Any switch between medications must be managed by your prescriber — do not attempt to change medications independently. There is no official established conversion chart. Your prescriber will assess the appropriate dose and timing if a switch is clinically indicated. This typically involves stopping one medication and starting the other on a new titration schedule.
Which medication's dosing schedule causes fewer side effects?
Side effects relate to the medication's mechanism and individual response, not necessarily the dosing schedule. Both medications commonly cause nausea, diarrhoea, and stomach discomfort, especially during dose escalation. These typically reduce over time. Your prescriber can advise on managing side effects and whether dose escalation adjustments might help.
Do I need a KwikPen prescription for both Wegovy and Mounjaro?
Yes, both are supplied as pre-filled KwikPen injection devices in the UK. Each pen contains 4 weekly doses. Both are prescription-only — you cannot obtain them without a valid prescription from your GP or a licensed private prescriber following a clinical assessment.
Ready to take control of your weight loss journey?
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