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 Chart for UK Adults
Mounjaro (tirzepatide) is prescribed as a once-weekly injection using a KwikPen device, with doses escalating gradually from 2.5mg to a maximum of 15mg. This guide explains the UK dosage schedule, how dose titration works, and what to expect at each stage. Understanding the dose progression helps you know what happens when you start treatment and how your prescriber monitors your response. Use our free BMI calculator to understand your starting eligibility, and our GLP-1 weight loss calculator to estimate 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.
How Mounjaro Dosage Works in the UK
Mounjaro is dispensed as a pre-filled KwikPen injector, with each pen containing four weekly doses. Your prescriber starts you on the lowest dose and increases it gradually every four weeks — this is called dose titration. The standard UK escalation schedule is:
- 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
- Weeks 21+: 15 mg once weekly (maximum maintenance dose)
You must spend at least four weeks on each dose before escalating. Some people stay on lower doses if they experience good weight loss results or tolerate the medication well. Your GP or specialist prescriber will assess your response and adjust accordingly. Clinical trial data shows average weight loss of approximately 15–21% body weight over the full dose range, though individual results vary significantly.
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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.
NHS Access and UK Eligibility for Mounjaro
In the UK, Mounjaro is available through NHS specialist weight management services (tier 3) or private prescription following online clinical assessment. NHS eligibility includes adults with BMI 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds. NICE has approved tirzepatide for use within NHS services, though regional availability and waiting lists vary significantly. Access through private prescribers does not require NHS referral and can be faster, with prescriptions dispensed by GPhC-registered pharmacies. Whichever route you choose, a licensed prescriber will assess whether Mounjaro is suitable for you individually.
- 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's the difference between Mounjaro and Wegovy dosing?
Mounjaro (tirzepatide) starts at 2.5mg and escalates to 15mg maximum. Wegovy (semaglutide) starts at 0.25mg and escalates to 2.4mg maximum. Mounjaro is a dual GIP/GLP-1 agonist while Wegovy is GLP-1 only. Both escalate over approximately 4–5 months. Approximate equivalent doses are roughly: Mounjaro 5mg ≈ Wegovy 0.5mg, Mounjaro 10mg ≈ Wegovy 1.7mg, and Mounjaro 15mg ≈ Wegovy 2.4mg, though these are not official conversions.
Can I skip a Mounjaro dose or reduce my dose?
Never skip a dose or self-reduce your Mounjaro dose without speaking to your prescriber. If you miss a dose by less than four days, take it as soon as you remember and continue your normal schedule. If more than four days have passed, skip that dose and take your next scheduled injection. Always contact your prescriber if you experience severe side effects — they may pause escalation or adjust your plan.
How long does it take to reach the full 15mg Mounjaro dose?
Following the standard NHS and private prescribing schedule, it takes approximately 20–24 weeks (5–6 months) to reach the full 15mg maintenance dose, starting from 2.5mg. Some people reach an effective dose before 15mg and remain on a lower maintenance dose if results are good. Your prescriber will monitor your progress and may adjust the timeline based on how you tolerate each dose.
What happens if side effects are severe at my current Mounjaro dose?
If you experience severe nausea, vomiting, constipation, or stomach pain, contact your prescriber immediately. They may recommend pausing dose escalation, staying on your current dose longer, or switching to a different approach. Some side effects naturally improve after a few weeks as your body adjusts. Never stop Mounjaro abruptly — always discuss changes with your prescriber.
Is Mounjaro available on the NHS in my area?
Mounjaro availability through the NHS depends on your regional Integrated Care Board (ICB) budget and local tier 3 weight management services. Some areas have limited access or longer waiting lists. Your GP can refer you to your local specialist service and advise on current availability. If NHS access is delayed, private prescription routes are available through licensed UK prescribers without needing an NHS referral.
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.