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
Free tracker included with every download this week
Using Mounjaro for Weight Loss — NHS & UK Guidance
Mounjaro (tirzepatide) is a prescription-only weight loss injection now available through NHS specialist services and private prescribing in the UK. While Mounjaro itself isn't a diet plan, it works most effectively when combined with reduced-calorie eating and increased physical activity. This guide explains how Mounjaro fits into a weight loss plan, NHS eligibility, and practical dietary approaches that support the medication's effects. Individual results vary, but clinical trials showed average weight loss of 15–21% of body weight alongside lifestyle changes.
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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 & How Mounjaro Supports Weight Loss
In the UK, Mounjaro is prescribed through NHS specialist tier 3 weight management services for adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds (BMI 27.5+) may apply due to higher health risks at lower BMI levels.
Mounjaro works by activating two natural hormone pathways (GIP and GLP-1) that regulate appetite, reduce food cravings, and help you feel fuller after smaller portions. This is why combining Mounjaro with a reduced-calorie diet plan is essential — the injection supports your ability to stick to dietary changes, but weight loss still requires a calorie deficit of roughly 500 kcal per day for sustainable results.
NHS eligibility is assessed by your GP, who refers you to a specialist service. Regional availability varies significantly — waiting lists can be several months in some areas. Check your local integrated care board (ICB) website for current access.
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.
Diet Planning & Practical Tips Alongside Mounjaro
There is no single "Mounjaro diet plan" — instead, focus on a balanced, reduced-calorie approach that works for you. The NHS recommends a deficit of 500 kcal per day for 0.5–1 kg per week loss. Mounjaro users often find it easier to eat smaller portions, so prioritise nutrient-dense foods: lean proteins, whole grains, vegetables, and healthy fats.
Start a food diary (paper or app-based) to track intake — many people on Mounjaro experience reduced appetite and may forget to eat enough protein, which risks muscle loss. Aim for at least 1.6–2.2g protein per kg body weight daily. Our free progress tracker helps you log weight changes week to week, and use our GLP-1 weight loss calculator to estimate projected outcomes at your Mounjaro dose.
- 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.
Can I get Mounjaro on the NHS in the UK?
Yes. Mounjaro is now approved by NICE for NHS use through specialist tier 3 weight management services. You need a referral from your GP and must meet eligibility criteria (BMI 30+ or 27+ with comorbidities). Availability and waiting times vary by region. Private prescription is also available via online assessment.
What's the difference between Mounjaro and a diet plan?
Mounjaro is a medication that supports appetite control and helps you stick to a diet plan — it's not a replacement for dietary change. Effective weight loss requires both the injection AND a reduced-calorie diet, typically 500 kcal below your maintenance intake, alongside increased physical activity.
How much weight will I lose on Mounjaro with a diet plan?
Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks, but individual results vary significantly. Most depends on your starting weight, adherence to dietary changes, activity level, and which dose you reach. Your GP or prescriber can give personalised expectations.
Do I need a formal diet plan PDF to use Mounjaro?
No formal PDF is required. Work with your prescriber or a dietitian to create a personalised approach: aim for a 500 kcal daily deficit, adequate protein (1.6–2.2g per kg), and whole foods. Many NHS services offer dietitian support; private providers vary.
What's the weekly weight loss injection called, and how does it differ from oral diets?
Mounjaro is a weekly weight loss injection (also called a "slimming jab"). Unlike oral diet plans alone, it actively regulates appetite hormones, making calorie deficit adherence easier for many people. The injection is most effective combined with dietary change and exercise — it amplifies, not replaces, lifestyle effort.
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.