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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Staying On 5mg Mounjaro vs Wegovy — What You Should Know
Many people starting weight loss medication wonder whether to increase their Mounjaro dose or switch to an alternative like Wegovy. If you're stable on 5mg Mounjaro, understanding how this compares to Wegovy can help you and your prescriber make the right choice for your health goals. This guide explains the clinical evidence, mechanism differences, and practical considerations for both options in the UK.
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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.
Clinical Evidence: SURMOUNT vs STEP Trial Data
Mounjaro (tirzepatide) at 5mg showed average weight loss of approximately 15% body weight in the SURMOUNT-1 clinical trial over 72 weeks, when combined with a reduced-calorie diet and increased physical activity. Wegovy (semaglutide) at its maximum dose of 2.4mg achieved approximately clinically studied weight loss in the STEP-1 trial over 68 weeks under similar conditions.
- Mounjaro uses a dual GIP and GLP-1 mechanism — activating two natural hormone pathways for appetite regulation
- Wegovy is a GLP-1 only receptor agonist — single mechanism, well-established in clinical practice
- Individual results vary considerably — some people respond better to one mechanism than the other
- Both are UK prescription-only medicines requiring clinical assessment before prescription
At 5mg, Mounjaro represents an intermediate dose in the titration schedule. Some people remain stable and achieve good results, whilst others continue escalating towards the 15mg maximum dose.
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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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Deciding Between Staying On 5mg or Switching — Key Factors
Your prescriber will consider your individual response, side effect profile, and health goals. Staying on 5mg Mounjaro may be appropriate if: you're achieving meaningful weight loss progress, side effects are manageable, and your GP feels further escalation is unnecessary. Switching to Wegovy might be considered if: you experience problematic side effects, prefer a single-mechanism approach, or your prescriber assesses it as more suitable for your health profile.
The choice is not about one being objectively "better" — it's about individual suitability. Both medications require ongoing clinical monitoring, regular check-ins with your prescriber, and consistent lifestyle changes. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses, and our BMI calculator to track your progress alongside any medication adjustments.
- 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 enough for weight loss?
Yes. In clinical trials, 5mg Mounjaro achieved average weight loss of around 15% body weight. However, individual results vary significantly. Some people need dose escalation, others remain stable on 5mg. Your prescriber will assess your personal response and adjust if needed based on your progress and tolerability.
Is Wegovy stronger than 5mg Mounjaro?
Not necessarily. Wegovy's maximum dose (2.4mg) achieved similar average weight loss (~14.9%) to 5mg Mounjaro (~15%) in clinical trials. The difference is mechanism, not strength. Mounjaro's dual GIP+GLP-1 action differs from Wegovy's single GLP-1 mechanism. Individual response varies — some people do better on one than the other.
What's the difference between Mounjaro and Wegovy in the UK?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. Wegovy (semaglutide) is GLP-1 only. Both are UK prescription-only once-weekly injections. Mounjaro starts at 2.5mg and escalates to 15mg maximum. Wegovy starts at 0.25mg, escalates to 2.4mg maximum. Both require clinical assessment before prescription.
Can I switch from Mounjaro to Wegovy?
Yes, but only with your prescriber's guidance. There's no official conversion chart between them, though approximate equivalences exist (5mg Mounjaro ≈ 0.5mg Wegovy). Any switch must be managed clinically — your prescriber will assess whether a switch is appropriate and manage the transition carefully to avoid treatment gaps.
Why would someone stay on 5mg instead of increasing Mounjaro?
Several reasons: achieving good weight loss results already, managing side effects better at a lower dose, personal health context, or prescriber assessment that further escalation isn't necessary. Medication management is individualised. Your GP or weight management specialist will review your progress and decide what's optimal for your health goals.
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.