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 Dosage for Weight Loss Explained
Mounjaro (tirzepatide) is a prescription-only weight loss injection available in the UK, with doses ranging from 2.5 mg to 15 mg once weekly. Understanding the dosage schedule is important if you're considering this treatment or have been prescribed it. This guide explains how Mounjaro dosing works, what clinical trials showed about effectiveness at different doses, and how prescribers adjust your dose over time. Our GLP-1 weight loss calculator above can help you explore potential outcomes at different doses.
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Calculate Your BMI Instantly
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 Dosage Schedule and Titration
Mounjaro is given as a once-weekly injection using a KwikPen device, with a structured dose escalation plan. You start at 2.5 mg for weeks 1–4, then increase to 5 mg for weeks 5–8. From there, your prescriber may escalate every 4 weeks: to 7.5 mg (weeks 9–12), 10 mg (weeks 13–16), 12.5 mg (weeks 17–20), and up to a maximum of 15 mg (week 21 onwards).
The stepping approach allows your body to adjust to the medication and helps your prescriber identify the lowest effective dose for you. Not everyone needs or tolerates the highest dose — many people achieve good weight loss results at 5 mg, 7.5 mg, or 10 mg. Your GP or specialist will assess how you're responding and whether you're experiencing manageable side effects before increasing further.
- 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+: 15 mg (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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Weight Loss Results at Different Mounjaro Doses
Clinical trial data from the SURMOUNT-1 study showed that weight loss effectiveness increases with dose escalation. At 5 mg weekly, participants lost an average of approximately 15% of their body weight over 72 weeks. At 10 mg, average loss increased to around 19.5%, and at the maximum 15 mg dose, average loss reached approximately 20.9%. However, individual results vary significantly — some people lose more, some less.
It's important to remember these are averages from clinical trials conducted alongside reduced-calorie diet and increased physical activity. Your own results will depend on your starting weight, metabolism, adherence to lifestyle changes, and how your body responds. Use our BMI calculator to track your current starting point, and our progress tracker to log changes over time as you take Mounjaro.
- 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 happens if I miss a Mounjaro injection?
If you miss a dose within 4 days of your scheduled injection day, take it as soon as you remember and continue your normal schedule. If more than 4 days have passed, skip that dose and take your next injection on your regular scheduled day. Never take two doses close together — maintain at least 72 hours (3 days) between injections.
Can my dose be reduced if I'm experiencing side effects?
Yes. If you're having difficult side effects like severe nausea or vomiting, speak to your prescriber. They may pause escalation, keep you on your current dose longer, or in some cases reduce your dose. Your health and tolerability matter — the goal is finding the dose that works for your body.
How long do I stay on each dose before it increases?
Each dose is maintained for a minimum of 4 weeks before escalation. This allows your body to adapt and helps your prescriber assess tolerability and effectiveness. Some people stay on the same dose longer if they're responding well and side effects are minimal.
Is Mounjaro available on the NHS for weight loss?
NICE has approved tirzepatide (Mounjaro) for NHS weight management services, but availability is limited to specialist tier 3/4 weight management services. Access varies by region and waiting lists can be long. Private access is available through GPhC-registered online prescribers following a clinical assessment.
How does Mounjaro dosage compare to Wegovy for weight loss?
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both once-weekly weight loss injections but use different mechanisms. Mounjaro is a dual GIP/GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Mounjaro's doses (2.5–15 mg) and Wegovy's doses (0.25–2.4 mg) are not directly comparable — they work differently. Your prescriber will advise which suits you.
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.