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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Mounjaro Tips and Tricks: How It Compares to Wegovy
If you're considering prescription weight loss treatment in the UK, you've likely heard about both Mounjaro and Wegovy. Both are once-weekly injections licensed for weight management, but they work differently and have distinct profiles. This guide explains the practical differences between tirzepatide (Mounjaro) and semaglutide (Wegovy) so you understand what each medication offers. A prescriber will assess which is suitable for you based on your individual health and circumstances.
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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.
Mounjaro vs Wegovy: Key Differences Explained
Mechanism of action is where these medications differ most. Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways to regulate appetite and blood sugar. Wegovy is a GLP-1-only agonist, working through a single hormone pathway. In clinical trials, this dual approach may contribute to slightly higher average weight loss with Mounjaro.
Clinical trial results from SURMOUNT (Mounjaro) showed average weight loss of approximately 20.9% at the maximum 15mg dose over 72 weeks, compared to STEP trials for Wegovy showing around 14.9% at the maximum 2.4mg dose. However, individual results vary significantly—some people respond better to one medication than the other. Both trials included participants following a reduced-calorie diet and increased physical activity.
Dosing schedules differ too. Mounjaro escalates from 2.5mg to 15mg over several months, whilst Wegovy escalates from 0.25mg to 2.4mg. Your prescriber will determine the appropriate dose based on your tolerance and response. Use our GLP-1 weight loss calculator to explore projected outcomes at different dose levels.
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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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Which Should You Choose? A Prescriber Decision
Neither Mounjaro nor Wegovy is inherently "better"—suitability depends on your individual health profile, previous medication responses, and what your prescriber recommends after clinical assessment. Some people prefer the dual mechanism of Mounjaro; others do equally well or better on Wegovy's single GLP-1 pathway. Both require a UK prescription following assessment by a licensed prescriber, whether through NHS specialist services or private online prescribing.
Practical tips for either medication:
- Start with the lowest dose and allow 4 weeks before escalating
- Stay hydrated and eat smaller, protein-rich meals to manage nausea
- Rotate injection sites weekly (abdomen, thigh, or upper arm)
- Keep pens refrigerated until first use, then room temperature for up to 30 days
- Track your progress with our free progress tracker to monitor weight loss alongside any lifestyle changes
- Report any persistent side effects to your prescriber
- 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 Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP + GLP-1 receptor agonist, activating two hormone pathways. Wegovy (semaglutide) activates only the GLP-1 pathway. This dual mechanism may contribute to Mounjaro's slightly higher average weight loss in clinical trials, but individual response varies. Both are prescription-only once-weekly injections licensed in the UK.
Which causes fewer side effects, Mounjaro or Wegovy?
Both medications have similar side effect profiles—nausea, diarrhoea, and constipation are most common. Individual tolerance varies considerably. Some people tolerate one better than the other. Starting at the lowest dose and escalating gradually over weeks helps minimise side effects. Your prescriber will monitor you and adjust your dose if needed.
Can my GP prescribe Mounjaro or Wegovy on the NHS?
NHS access is through specialist tier 3 weight management services, not routine GP prescription. You'll need an NHS referral from your GP to access these services, though waiting lists vary significantly by region. Private UK-licensed prescribers can also issue prescriptions following an online clinical assessment if you choose private treatment.
How long does it take to see weight loss results?
Most people notice appetite changes within the first 2–4 weeks. Measurable weight loss typically becomes visible around weeks 4–8. Clinical trials measured results over 68–72 weeks, so this is a sustained-use medication. Results are best maintained with ongoing diet and activity changes. Use our progress tracker to monitor your journey.
Is Mounjaro or Wegovy better for type 2 diabetes?
Both help with blood sugar control, but eligibility for weight loss treatment is based on BMI and weight-related health conditions, not diabetes diagnosis alone. If you have type 2 diabetes, your GP will assess which medication suits your overall health picture. Mounjaro and Wegovy work through different mechanisms, so your prescriber will recommend the most appropriate option for you.
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.