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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What Does 5mg Mounjaro Do? Comparison With Wegovy
A 5mg Mounjaro dose is the first maintenance dose most people reach after the initial 2.5mg starter phase. At this dose, Mounjaro may help reduce appetite and support weight loss as part of a reduced-calorie diet plan. To understand how 5mg Mounjaro compares to Wegovy, it's helpful to look at the clinical trial data and how these two prescription weight management medications work differently. Both are licensed for weight management in UK adults, but they use different mechanisms.
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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 5mg Mounjaro Compares to Wegovy — Mechanism and Trial Data
Mounjaro (tirzepatide) at 5mg is a dual GIP and GLP-1 receptor agonist — this dual mechanism is its key difference from Wegovy. In the SURMOUNT-1 clinical trial, participants on 5mg Mounjaro lost an average of approximately 15% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) uses a GLP-1-only mechanism and reaches its maximum dose of 2.4mg. In STEP-1 trials, participants on the maximum 2.4mg dose achieved approximately 14.9% average body weight loss at 68 weeks.
- 5mg Mounjaro is an intermediate dose — users can escalate further to 7.5mg, 10mg, 12.5mg, or 15mg
- Wegovy's 2.4mg is the maximum maintenance dose — no further escalation available
- Both require a prescription following clinical assessment
- Individual results vary significantly between people
The dual mechanism of Mounjaro may account for some clinical efficacy differences, though direct head-to-head trial comparisons have not been published in the UK market.
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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.
Eligibility, Prescription Access, and Personal Suitability
Both 5mg Mounjaro and Wegovy require prescription and clinical assessment — neither is available over the counter. In the UK, adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, or cardiovascular disease), may be eligible. However, a prescriber will assess your individual circumstances, medical history, and current medications to determine which medication — if either — is suitable for you.
You can access prescription weight loss treatment through NHS specialist tier 3 weight management services (following GP referral) or through private online prescribing. A licensed UK prescriber will guide your dose choice. Use our GLP-1 weight loss calculator to estimate potential outcomes, and our BMI calculator to check your starting point. Remember: both medications work best alongside sustained dietary changes and increased physical activity.
- 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 5mg Mounjaro equivalent to any Wegovy dose?
Approximately, 5mg Mounjaro is similar in clinical effect to Wegovy 1.7mg, though there is no official conversion chart. The dual GIP+GLP-1 mechanism of Mounjaro may provide different efficacy at the same weight-loss level. Any switch between medications must be managed by your prescriber.
How long does it take to reach 5mg Mounjaro?
The standard titration schedule is: 2.5mg for weeks 1–4, then 5mg from week 5 onwards. Each dose is given as a once-weekly injection via a KwikPen pre-filled device. If you tolerate 5mg well, your prescriber may continue this dose or escalate further based on your response and goals.
What are the main side effects of 5mg Mounjaro?
Very common side effects include nausea, diarrhoea, constipation, and stomach pain — these often decrease over time. Less common are injection site reactions, fatigue, and headache. Serious side effects are rare but include severe stomach pain (possible pancreatitis) or gallbladder problems. Report any severe symptoms to your GP immediately.
Can I get 5mg Mounjaro on the NHS in the UK?
Mounjaro is approved by NICE for NHS use within specialist tier 3 weight management services. Access varies significantly by region and waiting lists can be lengthy. Private prescribing is also available following an online clinical assessment. Your GP can discuss NHS referral or you can explore private options.
Why might my prescriber choose Wegovy instead of 5mg Mounjaro?
Your prescriber considers your medical history, current medications, kidney function, and personal preference. Wegovy may be recommended if you have certain health conditions, are already stabilised on a GLP-1 medication, or if Mounjaro is unavailable in your area. Both are prescription-only and require individualised clinical assessment.
Ready to take control of your weight loss journey?
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