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 — Complete UK Comparison
Wegovy and Mounjaro are both prescription-only weight loss injections available in the UK, but their dosing schedules are significantly different. Wegovy (semaglutide) starts at a much lower dose and escalates gradually over 16+ weeks, while Mounjaro (tirzepatide) begins at a higher starting dose with a similar titration timeline. Understanding these differences is essential if you're considering either medication, as the dosing approach reflects their different mechanisms and may affect how you experience the treatment. Both require a clinical assessment before prescription.
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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.
Wegovy Dosing Schedule and Escalation Timeline
Wegovy (semaglutide) is a once-weekly GLP-1 injection that starts at the lowest possible dose and escalates every 4 weeks. The standard dosing schedule is:
- Weeks 1–4: 0.25 mg
- Weeks 5–8: 0.5 mg
- Weeks 9–12: 1 mg
- Weeks 13–16: 1.7 mg
- Week 17+: 2.4 mg (maintenance/maximum dose)
The gradual escalation approach with Wegovy is designed to help your body adjust to the GLP-1 mechanism and reduce nausea during the early weeks. In clinical trials (STEP-1), participants at the maximum 2.4 mg dose achieved an average weight loss of approximately 14.9% of their body weight over 68 weeks, alongside a reduced-calorie diet and increased physical activity. This extended titration period means most people spend 4–5 months reaching their target dose.
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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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Mounjaro Dosing Schedule and Titration Approach
Mounjaro (tirzepatide) uses a different dosing strategy as a dual GIP and GLP-1 receptor agonist. The escalation timeline is:
- Weeks 1–4: 2.5 mg
- Weeks 5–8: 5 mg
- Weeks 9–12: 7.5 mg
- Weeks 13–16: 10 mg
- Weeks 17–20: 12.5 mg
- Week 21+: 15 mg (maximum dose)
Mounjaro's starting dose (2.5 mg) is higher than Wegovy's, and the maximum dose (15 mg) is substantially stronger. Clinical trial data (SURMOUNT-1) showed average weight loss of approximately 20.9% at the maximum 15 mg dose over 72 weeks. Your prescriber will adjust your Mounjaro KwikPen dose based on your tolerance and response, typically every 4 weeks. Both medications require an individual clinical assessment to determine if they're appropriate for you.
- 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 is the key difference between Wegovy and Mounjaro dosing?
Wegovy (semaglutide) starts at 0.25 mg and reaches a maximum of 2.4 mg over 16+ weeks. Mounjaro (tirzepatide) starts at 2.5 mg and reaches a maximum of 15 mg over 20+ weeks. Mounjaro's doses are numerically higher because it uses a dual GIP/GLP-1 mechanism, whereas Wegovy is a GLP-1 agonist only. Both escalate gradually every 4 weeks.
Which medication causes more side effects due to dosing?
Both medications commonly cause nausea, diarrhoea, and constipation during the escalation phase, particularly in the first 4–8 weeks. Wegovy's slower initial escalation (starting at 0.25 mg) may result in milder early side effects for some people, but individual responses vary significantly. Your prescriber will monitor your tolerance and adjust if needed.
Can you skip a dose or miss an injection with these medications?
If you miss a Wegovy or Mounjaro injection, take it within 4 days of the scheduled date and continue your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next injection on the normally scheduled day. Never take a double dose. Minimum time between doses is 72 hours.
How long does it take to reach the maximum dose on each medication?
Wegovy reaches maximum dose (2.4 mg) in approximately 16 weeks (4 months). Mounjaro reaches maximum dose (15 mg) in approximately 20 weeks (5 months). However, your prescriber may maintain you at a lower dose if you experience good weight loss results and wish to minimise side effects—maximum dose is not required for all patients.
Are Wegovy and Mounjaro interchangeable at equivalent doses?
No. Wegovy and Mounjaro are not directly interchangeable despite containing GLP-1 receptor agonist activity. Mounjaro's dual GIP/GLP-1 mechanism is different from Wegovy's single GLP-1 mechanism, and approximate dose equivalences (e.g., Mounjaro 5 mg ≈ Wegovy 0.5 mg) are clinical estimates only. Any switch between medications must be managed by your prescriber.
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