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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How Much Is 2.5 Mounjaro and How Does It Compare to Wegovy?
2.5 mg is the starting dose of Mounjaro (tirzepatide), a prescription-only weight management injection licensed in the UK. This initial dose is used for the first 4 weeks, after which your prescriber may increase it based on your response and tolerability. If you're comparing Mounjaro to Wegovy, the starting doses are quite different — Mounjaro begins at 2.5 mg whilst Wegovy starts at 0.25 mg. Both are once-weekly injections requiring a clinical assessment before prescription. Understanding these dose differences helps clarify how the two medications are used differently within UK weight management services. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
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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.
2.5mg Mounjaro vs Wegovy: Starting Doses and Mechanism Explained
2.5 mg Mounjaro is the lowest available dose and is designed as a starting point to allow your body to adjust to the medication. After 4 weeks at this dose, your prescriber will typically increase it gradually — the standard escalation schedule moves through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to the maximum of 15 mg weekly, with at least 4 weeks between increases.
Wegovy's starting dose is 0.25 mg — significantly lower than Mounjaro's 2.5 mg. This reflects the different mechanisms: Mounjaro is a dual GIP and GLP-1 receptor agonist (activating two hormone pathways), whilst Wegovy is a GLP-1 receptor agonist only (activating one pathway). The higher starting dose of Mounjaro still needs dose titration because individual tolerance varies.
- SURMOUNT-1 trial (Mounjaro): At the 15 mg maintenance dose, participants lost an average of approximately 20.9% body weight over 72 weeks alongside dietary and lifestyle changes
- STEP-1 trial (Wegovy): At the 2.4 mg maintenance dose, participants lost an average of approximately 14.9% body weight over 68 weeks with the same lifestyle support
These are clinical trial averages — individual results vary considerably. Both medications require a clinical assessment to determine suitability based on your personal health circumstances.
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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.
Which Dose Is Right for You? Clinical Assessment and Eligibility
Neither 2.5 mg Mounjaro nor any Wegovy dose should be self-selected. Your prescriber will assess your eligibility based on NHS criteria: a BMI of 30 kg/m² or above, or 27 kg/m² or above if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply.
Your individual health history, current medications, and treatment goals determine which medication and which dose sequence is appropriate. Some people start and remain on Mounjaro; others escalate through all dose levels. Some are prescribed Wegovy instead. This is a personalised clinical decision.
Calculate your current BMI using our free BMI calculator above to understand where you fall on NHS weight categories, then discuss medication options with your GP or a licensed prescriber through an appropriate clinical channel.
- 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.
Is 2.5 mg Mounjaro an effective weight loss dose?
2.5 mg is the starting dose designed to allow your body to adjust to the medication. It is not a maintenance dose — your prescriber will typically increase it every 4 weeks. Clinical trial results come from higher maintenance doses (up to 15 mg), not from 2.5 mg alone. Individual responses vary.
How quickly does Mounjaro 2.5 mg work?
Most people experience some appetite suppression within 1–2 weeks of starting 2.5 mg, though significant weight loss typically occurs once you reach higher maintenance doses after several months of titration. Results are highly individual.
Can I stay on 2.5 mg Mounjaro long-term?
2.5 mg is designed as a short-term starting dose, not a maintenance dose. Your prescriber will assess whether to increase your dose every 4 weeks based on your tolerance and response. Staying at 2.5 mg long-term is not standard practice.
What is the main difference between Mounjaro and Wegovy starting doses?
Mounjaro begins at 2.5 mg weekly, whilst Wegovy starts at 0.25 mg weekly. This reflects their different mechanisms — Mounjaro activates two hormone pathways (GIP and GLP-1) whilst Wegovy activates one (GLP-1 only). Both require dose titration over weeks or months.
How do I get a Mounjaro prescription in the UK?
Mounjaro is prescription-only and requires a clinical assessment. Access is through NHS specialist tier 3 weight management services (via GP referral, though waiting lists vary by region) or through private prescribing via a licensed UK prescriber online. Either route requires professional eligibility assessment.
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.