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 5.0 Mg vs Wegovy — What's the Difference?
Mounjaro 5.0 mg and Wegovy are both prescription-only weight management injections available in the UK, but they work differently. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) activates only the GLP-1 pathway. At the 5.0 mg dose, Mounjaro represents an early maintenance stage, whereas Wegovy's maximum dose is 2.4 mg. Both require clinical assessment and work alongside lifestyle changes. This guide compares the two to help you understand the key differences. Check your personal BMI using our free BMI calculator to see whether you might be eligible for either medication.
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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.
How Mounjaro and Wegovy Work — Mechanism Comparison
Mounjaro (tirzepatide) activates two hormone pathways simultaneously: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual mechanism may help regulate appetite, reduce food cravings, and support feeling fuller after meals more comprehensively than single-pathway medications.
Wegovy (semaglutide) activates only the GLP-1 pathway. It signals fullness to the brain and slows gastric emptying, but uses a single mechanism rather than a dual approach.
In clinical trials, the SURMOUNT-1 study showed Mounjaro at the 5.0 mg dose helped participants lose an average of approximately 15% of body weight over 72 weeks. The STEP-1 trial showed Wegovy at its maximum 2.4 mg dose achieved approximately clinically studied weight loss. Results vary significantly between individuals, and both medications are used alongside a reduced-calorie diet and increased physical activity.
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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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Doses, Eligibility, and Individual Suitability
Mounjaro escalates from 2.5 mg to a maximum of 15 mg weekly, with the 5.0 mg dose typically used during the escalation phase. Wegovy reaches its maximum at 2.4 mg weekly. Both are prescribed through UK specialist weight management services or private online assessment.
Eligibility requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Whether Mounjaro or Wegovy is more suitable depends on your individual health profile, medical history, and how your prescriber assesses your response to treatment. Neither medication is "better" — the choice is personal. A licensed prescriber will assess which is appropriate for you following a clinical consultation. Use our GLP-1 weight loss calculator to explore projected outcomes with different medications and doses.
- 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 Mounjaro 5.0 mg stronger than Wegovy 2.4 mg?
Mounjaro 5.0 mg and Wegovy 2.4 mg use different mechanisms and doses cannot be directly compared. Mounjaro uses a dual GIP+GLP-1 mechanism, while Wegovy uses GLP-1 only. Clinical trial results show both help participants lose approximately 15% body weight on average, though individual results vary. Your prescriber will advise which is more suitable for you.
Can I switch from Wegovy to Mounjaro?
Switching between medications is possible but must be managed by your prescriber. There is no official conversion chart between Mounjaro and Wegovy doses. If you and your prescriber decide to switch, they will assess the appropriate starting dose and escalation plan based on your individual response and health profile.
How long does Mounjaro 5.0 mg take to work?
Most people taking Mounjaro notice appetite reduction and early weight loss effects within 2–4 weeks at the 5.0 mg dose. However, maximum benefit typically takes 8–12 weeks at each dose level as your body adjusts. Consistent use alongside dietary changes and physical activity produces the best results.
Is Mounjaro available on the NHS in the UK?
Mounjaro (tirzepatide) is approved by NICE for use within NHS specialist tier 3 weight management services. However, NHS availability varies significantly by region and ICB. Waiting lists can be lengthy. Private online assessment and prescription is also available through GPhC-registered pharmacies, typically taking days rather than months.
What are the main side effects of Mounjaro 5.0 mg?
Common side effects at the 5.0 mg dose include nausea, diarrhoea, constipation, and stomach discomfort. Most are mild and tend to reduce as your body adjusts. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or allergic reactions. Always report persistent or concerning symptoms to your prescriber.
Ready to take control of your weight loss journey?
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