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 Right Dose of Mounjaro in the UK?
Mounjaro (tirzepatide) is available in escalating doses from 2.5 mg up to 15 mg, administered as a once-weekly injection via a KwikPen device. In the UK, treatment begins at the lowest dose and increases gradually over weeks to find the most effective and tolerable dose for each individual. This article explains the NHS prescribing context, dose titration schedule, and how UK eligibility for Mounjaro through specialist services works, alongside practical information about what to expect from the escalation process.
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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.
NHS Mounjaro Dosing Schedule and Eligibility
Mounjaro doses escalate in a structured schedule:
- 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 escalation requires a minimum of 4 weeks at the previous dose. In the UK, Mounjaro is prescription-only and accessed through NHS tier 3 specialist weight management services following a clinical assessment. NICE approved tirzepatide for use within these services, but availability varies significantly by region and ICB. Your prescriber will assess whether dose escalation is appropriate for you based on weight loss response and side effect tolerance. Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, may be eligible. Our GLP-1 weight loss calculator can help you understand potential results across different doses.
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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 vs Private Access and Dose Context
In the UK, Mounjaro access differs between NHS and private routes. NHS route: referral to specialist tier 3 services through your GP, assessment by a multidisciplinary team, and prescription if clinically suitable—but waiting lists can be lengthy and regional access varies. Private route: online consultation with a UK-licensed prescriber, prescription issued if appropriate, dispensed by a GPhC-registered pharmacy—faster access but costs typically range from £129–£320+ monthly depending on dose. Clinical trial data (SURMOUNT-1) showed average weight loss of approximately 15–21% body weight across the dosing range, though individual results vary considerably. Both routes require a prescription and clinical assessment. Use our BMI calculator above to check your starting point and discuss your personal eligibility and dose options with your GP or a licensed prescriber.
- 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 starting dose of Mounjaro in the UK?
The starting dose is 2.5 mg once weekly. This is used for the first 4 weeks to allow your body to adjust. Your dose is then escalated by 2.5 mg every 4 weeks if tolerated, up to a maximum of 15 mg weekly. Your prescriber will decide the pace of escalation based on your response and side effects.
How long does it take to reach the maximum Mounjaro dose?
Reaching the maximum 15 mg dose takes approximately 20 weeks if escalating every 4 weeks without delays. However, many people remain on lower doses if they achieve good results—there is no requirement to reach 15 mg. Your prescriber will work with you to find your optimal dose.
Is Mounjaro available on the NHS in the UK?
Yes, NICE approved tirzepatide (Mounjaro) for use within NHS specialist tier 3 weight management services. However, access varies by region. You will need a GP referral to a specialist service, and waiting lists can be long. Private access is also available through UK-licensed prescribers without NHS referral.
Can my Mounjaro dose be paused or reduced?
Yes. If you experience significant side effects or wish to pause treatment, your prescriber can hold your dose or reduce it. If you stop for 4 weeks or longer and restart, you typically return to a lower dose and re-titrate. Always discuss changes with your prescriber—do not adjust doses independently.
What does Mounjaro vs Wegovy tell us about dosing?
Mounjaro is a dual GIP/GLP-1 agonist with a maximum dose of 15 mg weekly, while Wegovy (semaglutide, GLP-1 only) has a maximum of 2.4 mg weekly. The different mechanisms and dose ranges reflect different formulations. Clinical trials show similar average weight loss outcomes (~15–21%), but individual responses vary. Your prescriber will advise which is appropriate for you. ```
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