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 is the Highest Mounjaro Dose?
The highest Mounjaro dose available in the UK is 15 mg, injected once weekly. Mounjaro (tirzepatide) is a prescription-only GIP and GLP-1 receptor agonist licensed for weight management in UK adults. However, most people do not start at the highest dose — instead, doses are gradually increased over several months to allow your body to adjust and to find the most effective dose for you personally. Your prescriber will assess your individual response and tolerability before considering escalation to higher doses.
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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 Dose Titration Works
Mounjaro is prescribed using a dose titration schedule, which means you start at a low dose and gradually increase it every 4 weeks. Here is the standard UK dosing escalation pathway:
- Weeks 1–4: 2.5 mg once weekly (starting dose)
- Weeks 5–8: 5 mg once weekly
- Weeks 9–12: 7.5 mg once weekly
- Weeks 13–16: 10 mg once weekly
- Weeks 17–20: 12.5 mg once weekly
- Week 21+: 15 mg once weekly (maximum dose)
Each dose is given as a single injection using a pre-filled KwikPen device. You must spend a minimum of 4 weeks on each dose before your prescriber will consider increasing it further. This gradual approach helps reduce side effects like nausea and allows your body to adapt. Not everyone needs to reach the highest dose — many people find their best results at 10 mg or 12.5 mg, and some prescribers may recommend staying at a lower maintenance dose if you are tolerating it well and achieving good results.
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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.
Why Not Everyone Reaches 15 mg
Although 15 mg is the maximum approved dose in the UK, it is not always the right dose for everyone. Clinical trial data suggests that weight loss improvements continue incrementally as doses increase, but the difference between 12.5 mg and 15 mg is relatively modest for many people. Your prescriber will consider your individual tolerability, side effect profile, and weight loss response when deciding whether to escalate further. If you are experiencing significant side effects at a lower dose, or if you are already achieving satisfactory results, your prescriber may recommend staying at your current dose rather than continuing to increase. This personalised approach means the "highest dose" for you might be 10 mg, not 15 mg — and that is medically appropriate.
- 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 highest Mounjaro dose in the UK?
The highest approved Mounjaro dose is 15 mg, injected once weekly. This is the maximum dose licensed for weight management in UK adults with a BMI of 30 or above, or 27 or above with weight-related health conditions.
How long does it take to reach the highest Mounjaro dose?
It takes a minimum of 20 weeks to reach 15 mg if you escalate every 4 weeks without delay. However, many people remain on lower doses (10 mg or 12.5 mg) long-term if they tolerate and respond well to those doses.
Will I definitely need to go up to 15 mg?
No. Your prescriber will assess your response, weight loss, and side effects at each dose level. Many people achieve good results at 10 mg or 12.5 mg and do not escalate further. The dose is personalised to your individual needs.
What if I cannot tolerate higher doses of Mounjaro?
If you experience significant side effects at higher doses, inform your prescriber. You may remain on a lower maintenance dose that you tolerate well. Some people find 5 mg or 7.5 mg is their optimal dose, and that is medically appropriate.
How does Mounjaro's highest dose compare to Wegovy?
Mounjaro's maximum dose is 15 mg weekly, whilst Wegovy (semaglutide) maxes out at 2.4 mg weekly. Although the numbers appear very different, they are different medication types — Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy is a GLP-1 agonist only. Clinical trial results cannot be directly compared between the two.
Ready to take control of your weight loss journey?
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