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
Free tracker included with every download this week
Mounjaro vs Wegovy: Dosage Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available in the UK, but they use different dosing schedules. Mounjaro starts at 2.5 mg and escalates weekly up to 15 mg, whilst Wegovy begins at 0.25 mg and increases to a maximum of 2.4 mg. Understanding the differences in dosing, escalation timelines, and mechanism can help you discuss options with your GP or prescriber. Both medications require a clinical assessment before prescription, and individual suitability depends on your personal health profile.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Dosage Schedules: Week-by-Week Comparison
Mounjaro (tirzepatide) uses a rapid dose escalation over 16+ weeks. Starting at 2.5 mg weekly, it increases by 2.5 mg every four weeks: 5 mg (weeks 5–8), 7.5 mg (weeks 9–12), 10 mg (weeks 13–16), 12.5 mg (weeks 17–20), and finally 15 mg at week 21+. Each KwikPen contains four weekly doses.
Wegovy (semaglutide) uses a slower escalation over 16+ weeks. It begins at 0.25 mg weekly for four weeks, then increases to 0.5 mg (weeks 5–8), 1 mg (weeks 9–12), 1.7 mg (weeks 13–16), and reaches maximum dose of 2.4 mg at week 17+. This gentler escalation may reduce gastrointestinal side effects for some users.
Both require a minimum of four weeks at each dose before escalation. Neither should be adjusted without prescriber guidance.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Mechanism, Efficacy, and Individual Suitability
Mechanism difference: Mounjaro is a dual GIP and GLP-1 receptor agonist, activating two hormone pathways simultaneously. Wegovy is a GLP-1 receptor agonist only, activating one pathway. Clinical trials (SURMOUNT for Mounjaro, STEP for Wegovy) showed average weight loss of approximately 15–21% for Mounjaro and approximately 15% for Wegovy—though individual results vary considerably.
Prescriber selection depends on your health profile, previous medication responses, and contraindications. Your GP or licensed prescriber will assess which medication—if either—is appropriate for you. Try our free GLP-1 weight loss calculator to explore estimated outcomes, and use the BMI calculator to understand your current health category.
- 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 starting dose for each medication?
Mounjaro starts at 2.5 mg once weekly. Wegovy starts at 0.25 mg once weekly. Both are injected subcutaneously (under the skin) on the same day each week. Your prescriber will provide injection guidance.
How long does dosage escalation take?
Both medications escalate over approximately 16–20 weeks to reach maintenance or maximum dose. Mounjaro increases every four weeks by 2.5 mg steps. Wegovy increases every four weeks in smaller increments (0.25–0.5 mg steps). Neither should be rushed.
Can you skip a dose increase if side effects occur?
Yes. If side effects like nausea are difficult to manage, you can remain on your current dose longer before escalating. Always contact your prescriber before making any changes—do not adjust doses independently.
Which medication reaches its maximum dose faster?
Mounjaro escalates to 15 mg over 20+ weeks with larger step increases (2.5 mg jumps). Wegovy reaches 2.4 mg over 16+ weeks with smaller increments. Mounjaro's higher dose reflects its dual mechanism; Wegovy's lower maximum reflects its single GLP-1 pathway.
Does a higher maximum dose mean better results?
Not necessarily. Clinical trial results showed that higher doses of each medication produced greater average weight loss, but individual responses vary significantly. Your prescriber will determine the appropriate dose based on your tolerance, efficacy, and health needs—not maximum dose alone.
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.