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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How Mounjaro Supports Weight Loss in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK. It works as a dual GIP and GLP-1 receptor agonist, helping to regulate appetite and support feeling fuller after meals. This guide explains how Mounjaro may help with weight, NHS eligibility criteria, NICE guidance, and whether it's right for you in a UK context. We'll cover the prescription process, expected outcomes from clinical trials, and how it compares to other weekly weight loss injections available in the UK.
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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 Eligibility and NICE Guidance for Mounjaro in the UK
NICE has approved tirzepatide (Mounjaro) as a treatment option within NHS specialist weight management services. To be eligible for Mounjaro through the NHS, you typically need a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or sleep apnoea.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds (BMI 27.5 and above) due to higher health risks at these levels. Access is through tier 3 specialist weight management services via NHS referral from your GP — not through standard primary care. Regional availability varies significantly, and waiting times can be substantial in many areas. Check our free BMI calculator to determine where you fall on NHS thresholds, and discuss eligibility with your GP.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 Routes: How to Access Mounjaro in the UK
NHS route: Referral to a tier 3 weight management service, clinical assessment, and prescription. This can involve waiting lists of months to over a year depending on your region. Mounjaro is provided at NHS cost once approved.
Private route: Online consultation with a UK-licensed prescriber, clinical assessment, and prescription through a GPhC-registered pharmacy if suitable. Available without NHS referral, typically accessible within days. Costs range from around £129–£320 monthly depending on dose. Clinical trials showed Mounjaro helped participants lose an average of 15–21% body weight alongside diet and exercise — though individual results vary. Use our GLP-1 weight loss calculator to estimate potential outcomes, and track your progress with our free progress tracker.
- 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 average weight loss with Mounjaro in UK clinical trials?
In the SURMOUNT-1 trial, participants on the maximum 15mg dose lost approximately 20.9% of their body weight over 72 weeks alongside a reduced-calorie diet and increased activity. At 5mg, average loss was around 15%. Individual results vary significantly based on starting weight, lifestyle changes, and individual metabolism. Always discuss realistic expectations with your healthcare provider.
Do I need to be on the NHS to get Mounjaro in the UK?
No. You can access Mounjaro through either NHS specialist services (via GP referral to tier 3) or private prescription through an online UK-licensed prescriber. NHS access involves assessment and potential waiting times. Private access is faster but involves costs. Both routes require clinical assessment to confirm suitability.
What dose of Mounjaro would I start on in the UK?
The standard starting dose is 2.5mg per week for the first 4 weeks. Your prescriber will assess whether to increase doses every 4 weeks (to 5mg, 7.5mg, 10mg, 12.5mg, then 15mg maximum). Dose escalation depends on your response, side effects, and clinical judgment. Your prescriber will guide this throughout treatment.
How does Mounjaro compare to Wegovy for weight loss?
Both are once-weekly injections licensed for UK weight management. Mounjaro is a dual GIP+GLP-1 agonist (average loss 15–21%), while Wegovy is GLP-1 only (average loss around 15%). Mounjaro may work slightly differently due to dual action, but clinical effectiveness is similar. Wegovy typically starts at a lower dose (0.25mg). Prescriber assessment determines which is more appropriate for you.
Will the NHS pay for Mounjaro if I get it privately first?
This varies by NHS region and local integrated care board (ICB) policy. Some regions may support continuation if you've started privately; others may not. It's essential to discuss with your GP before accessing private treatment, as this may affect future NHS eligibility or funding decisions in your area.
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.