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 Dose — How Much and When to Take It
Mounjaro (tirzepatide) is a prescription-only weight management injection available in the UK that's taken once weekly. The medication comes in a pre-filled KwikPen device and requires a structured dosing schedule, starting at 2.5 mg and potentially increasing to a maximum of 15 mg weekly. Understanding how Mounjaro dosing works is essential if you're considering this treatment or have been prescribed it by your GP or a licensed healthcare professional. Your dose may be adjusted gradually based on your response to treatment and how you tolerate the 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.
Mounjaro Dose Schedule: Week-by-Week Breakdown
Mounjaro is administered in a structured dose titration schedule, meaning your dose gradually increases over several weeks to help minimise side effects and allow your body to adapt. Each dose is a once-weekly injection, and you stay on each dose for a minimum of 4 weeks before potentially moving to the next level.
- Weeks 1–4: 2.5 mg (starting dose)
- Weeks 5–8: 5 mg (first escalation)
- Weeks 9–12: 7.5 mg (second escalation)
- Weeks 13–16: 10 mg (third escalation)
- Weeks 17–20: 12.5 mg (fourth escalation)
- Week 21 onwards: 15 mg (maximum maintenance dose)
Your prescriber may adjust this schedule based on your individual response. Some people stay on a lower maintenance dose (such as 10 mg) if they're achieving good results without excessive side effects. Your GP or prescriber will review your progress regularly.
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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.
Clinical Effectiveness and Expected Results
Clinical trials (SURMOUNT-1) showed that Mounjaro helped participants lose varying amounts of weight depending on their dose: approximately clinically studied weight loss at 5 mg, around 19.5% at 10 mg, and roughly 20.9% at the 15 mg maximum dose. However, individual results vary significantly, and weight loss is achieved alongside a reduced-calorie diet and increased physical activity. Losing weight at a sustainable rate of 0.5–1 kg per week is typical. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses, though your actual results will depend on your personal circumstances, adherence to lifestyle changes, and how your body responds to the medication.
- 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.
Can I jump straight to the 15 mg dose?
No. Mounjaro requires dose titration for safety and tolerability. You must stay on each dose for at least 4 weeks before increasing. Starting at 2.5 mg and escalating gradually helps your body adapt and reduces the risk of severe side effects like nausea or vomiting. Your prescriber will not accelerate this schedule without specific clinical reasons.
What happens if I can't tolerate my current dose?
If you experience severe side effects, your prescriber may pause escalation and keep you on your current dose longer, or in rare cases reduce your dose. Many side effects like nausea improve after a few weeks on the same dose as your body adjusts. Always inform your prescriber of any concerning symptoms before your next injection.
Is 15 mg always the target dose?
No. Some people achieve their weight loss goals on 10 mg or 12.5 mg and don't need to escalate further. Your prescriber will assess whether increasing to 15 mg is necessary based on your weight loss progress, side effects, and overall health. Lower maintenance doses are perfectly acceptable if they're working for you.
How long do I stay on each dose before it's increased?
You must remain on each dose for a minimum of 4 weeks. This allows time to assess how you're tolerating the medication and how your body is responding. After 4 weeks, your prescriber will review whether it's safe and appropriate to escalate to the next dose level.
What dose is available on the NHS in the UK?
Mounjaro is now approved by NICE for NHS use within specialist weight management services (tier 3). However, NHS availability varies significantly by region (integrated care boards). Private prescribing offers more consistent access across the UK without waiting lists. Your GP can advise on NHS options in your area or discuss private prescribing alternatives.
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.