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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5th Dose Mounjaro Pen vs Wegovy — How They Compare
By the time you reach the 5th dose of Mounjaro, you're typically moving towards the higher dose range where significant clinical outcomes emerge. If you're wondering how this compares to Wegovy, the key differences lie in the mechanism of action, dose titration schedules, and individual suitability. Both are prescription-only weight management injections licensed in the UK, but they work differently. Understanding these differences helps you and your prescriber make an informed decision about which might be more appropriate for your 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: Mechanism and Dosing Schedules
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways simultaneously, which sets it apart from Wegovy. The KwikPen contains four weekly doses, so your 5th dose occurs during the second pen. Mounjaro's dose schedule is: 2.5 mg (weeks 1–4), 5 mg (weeks 5–8), 7.5 mg (weeks 9–12), 10 mg (weeks 13–16), and 12.5 mg (weeks 17–20), with 15 mg as the maximum at week 21 onwards. Your 5th dose would therefore be 10 mg, typically reached around week 17.
Wegovy (semaglutide) is a single GLP-1 receptor agonist — it targets one hormone pathway. The dose escalation is: 0.25 mg (weeks 1–4), 0.5 mg (weeks 5–8), 1 mg (weeks 9–12), 1.7 mg (weeks 13–16), and 2.4 mg (week 17 onwards). At your 5th dose on Wegovy, you'd typically be at 1.7 mg. The SURMOUNT-1 clinical trial showed Mounjaro achieved approximately 20.9% average body weight loss at the maximum 15 mg dose, whilst the STEP-1 trial showed Wegovy at 2.4 mg achieved approximately 14.9% average weight loss — though individual results vary significantly, and these figures were achieved alongside 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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Which Is Right for You? Prescriber Assessment Matters
Your prescriber will determine which medication is suitable based on your individual health profile, medical history, and response to treatment. Both Mounjaro and Wegovy are prescription-only and require clinical assessment before and during treatment. If you've tolerated earlier doses of Mounjaro well and are approaching the 5th dose, your prescriber may continue you on this medication. If you're considering switching from one to the other, this must be done under medical supervision — there is no automatic conversion between them. You can use our free GLP-1 weight loss calculator to explore potential weight loss ranges with either medication, and our BMI calculator to track your progress at each dose increase.
- 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 is the 5th dose of Mounjaro?
The 5th weekly injection of Mounjaro KwikPen is typically 10 mg, reached around week 17 of treatment. Each pen contains four doses, so your 5th dose comes during your second pen. This is part of the standard dose titration schedule, with escalations every 4 weeks.
How does Mounjaro's 5th dose compare to Wegovy at the same timepoint?
At week 17, Mounjaro reaches 10 mg whilst Wegovy reaches 1.7 mg. Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is GLP-1-only. Clinical trials showed different weight loss outcomes, but individual response varies. Your prescriber will assess which suits you better.
Can I switch from Mounjaro to Wegovy at the 5th dose?
Switching between medications requires prescriber guidance. There is no established conversion chart between Mounjaro and Wegovy doses. Any switch must be managed medically to ensure safe transition and continued efficacy.
What side effects might I experience at Mounjaro's 5th dose?
Common side effects include nausea, diarrhoea, vomiting, and constipation. At the 10 mg dose, these may be less pronounced than at lower doses as your body may have adapted. Always report persistent or severe symptoms to your prescriber.
How is the 5th dose of Mounjaro prescribed in the UK?
Mounjaro is prescription-only and available through NHS specialist weight management services or private online prescribing with a UK-licensed prescriber. Your prescriber will assess eligibility (BMI ≥30, or ≥27 with weight-related health conditions) and suitability before continuing to higher doses.
Ready to take control of your weight loss journey?
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