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
What Is The Mounjaro Diet?
There is no specific "Mounjaro diet" — Mounjaro (tirzepatide) is a prescription-only weight management injection that works alongside any reduced-calorie diet you choose. It's a dual GIP and GLP-1 receptor agonist that may help reduce appetite and support feeling fuller after meals. In the UK, Mounjaro is prescribed for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. The medication isn't a replacement for dietary changes — it's a tool to support them. This guide explains how Mounjaro works with diet and what realistic expectations are.
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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 Works With Diet
Mounjaro doesn't prescribe a specific diet plan. Instead, it activates two natural hormone pathways — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) — that help regulate appetite and reduce food cravings. This means you may feel fuller after smaller meals and experience fewer cravings between meals, making it easier to maintain a reduced-calorie diet of your choice.
Clinical trials showed that Mounjaro helped participants lose an average of 15–21% of their body weight over 72 weeks — but this was achieved alongside a reduced-calorie diet and increased physical activity, not Mounjaro alone. The medication amplifies the effects of the dietary changes you make, rather than doing the work for you.
You can follow any dietary approach — Mediterranean diet, low carbohydrate, intermittent fasting, or traditional calorie counting. The NHS recommends a sustainable deficit of around 500 kcal per day, which typically results in a loss of approximately 0.5–1 kg per week. Your GP or prescriber can signpost you to a dietitian or weight management support programme.
Clinically BackedWeight Loss
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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.
Mounjaro UK Prescription and Eligibility
Mounjaro (tirzepatide) is prescription-only in the UK and requires a clinical assessment before being prescribed. Access is available through NHS specialist weight management services (tier 3/4) or through private online prescribing from a UK-licensed prescriber.
You may be eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease. If you are of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds (from BMI 27.5) may apply, as these populations face higher health risks at lower weights.
Doses range from 2.5 mg to 15 mg, administered once weekly via a KwikPen injection. You can use our free GLP-1 weight loss calculator to estimate potential weight loss at different doses — though individual results vary significantly.
- 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.
Is there a specific Mounjaro diet I must follow?
No. Mounjaro works alongside any reduced-calorie diet you choose — whether Mediterranean, low carb, or calorie counting. The medication helps reduce appetite and cravings, making it easier to stick to a diet of your choice. Your GP or prescriber may recommend referral to a dietitian for personalised guidance.
How much weight can I expect to lose on Mounjaro?
Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks when combined with diet and exercise. However, individual results vary significantly. Use our GLP-1 weight loss calculator to estimate potential loss at your dose, but this is a projection — not a assures.
Do I need to exercise while taking Mounjaro?
Exercise isn't mandatory but is recommended. The NHS advises 150 minutes of moderate-intensity activity per week. Mounjaro works best alongside both dietary changes and increased physical activity. Your GP can advise on safe exercise options for your health.
Can I use Mounjaro if I have type 2 diabetes?
Yes. Mounjaro is licensed for weight management in adults with a BMI of 27 or above who have weight-related health conditions including type 2 diabetes. However, if you're taking diabetes medications like insulin or sulphonylureas, your prescriber may need to adjust doses — discuss this with your GP.
How do I know if I'm eligible for Mounjaro on the NHS?
Contact your GP. NHS eligibility criteria include BMI 30 or above, or BMI 27–29.9 with weight-related health conditions. Your GP will assess you and refer to a specialist weight management service (tier 3) if appropriate. NHS availability varies by region — waiting times can be significant in some areas.
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.