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
How Many Calories Do You Eat On Mounjaro?
Mounjaro (tirzepatide) doesn't set a specific calorie limit — instead, it reduces your appetite, so you naturally eat fewer calories without strict counting. Most people taking Mounjaro on the NHS or privately consume around 1,200–1,800 kcal daily, though this varies significantly based on individual metabolism, starting weight, and lifestyle. The medication works alongside a reduced-calorie diet and increased physical activity for best results. Your GP or prescriber will discuss realistic calorie targets during your clinical assessment and throughout your treatment.
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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 Affects Appetite and Calorie Intake
Mounjaro is a dual GIP and GLP-1 receptor agonist that works by signalling to your brain that you're fuller after smaller portions. This means you're less likely to feel hungry between meals and may naturally reduce your calorie intake without strict dieting. In clinical trials, people taking Mounjaro reported reduced food cravings and a genuine sense of satiety on smaller meals.
The SURMOUNT-1 trial showed that participants lost an average of 15–21% of their body weight over 72 weeks — achieved through both the appetite-suppressing effect of the medication and adherence to a modest calorie deficit (typically 500–750 kcal below maintenance). However, results vary significantly between individuals. Some people naturally gravitate toward 1,400 kcal daily, others toward 1,600 kcal, depending on their appetite suppression response and lifestyle.
Your prescriber won't typically mandate a specific calorie count. Instead, they'll advise eating a balanced diet with adequate protein, fibre, and nutrients — and letting Mounjaro's appetite-suppressing effect guide your portions. This approach is more sustainable than strict calorie restriction alone.
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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.
Calorie Intake on Mounjaro: NHS and Practical Guidelines
The NHS emphasises that weight loss medications like Mounjaro (available through specialist tier 3 weight management services) are most effective when combined with sustainable dietary changes and increased physical activity — not extreme calorie cutting. A typical approach involves eating balanced, whole foods, staying hydrated, and aiming for a calorie deficit of around 500 kcal daily, which supports loss of approximately 0.5 kg per week.
Common side effects of Mounjaro — including nausea, reduced appetite, and changes in taste — may further reduce how much you feel like eating in your first weeks. This is temporary for most people. If you're struggling with very low calorie intake or severe nausea, contact your GP immediately, as this may indicate a dose adjustment is needed.
Track your weight loss progress and how you feel using our free progress tracker, and discuss realistic calorie and meal targets with your prescriber. Individual circumstances differ — age, metabolism, activity level, and other medications all affect how many calories you need.
- 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.
Does Mounjaro set a strict calorie limit?
No. Mounjaro doesn't require a specific calorie count — it reduces appetite so you naturally eat less. Most people fall into a 1,200–1,800 kcal range, but your actual intake depends on your body's response and activity level. Your prescriber will discuss realistic targets during assessment.
How many calories should I aim for on Mounjaro?
The NHS recommends a calorie deficit of around 500 kcal daily for sustainable weight loss. Your exact target depends on your starting weight, metabolism, and activity. A GP or dietitian can provide personalised guidance. Never drop below 1,200 kcal without medical supervision.
Why do I eat so little on Mounjaro?
Mounjaro activates appetite-regulating pathways in your brain, signalling fullness after smaller meals. This is the intended effect — it's not forced undereating. If you feel unwell or are struggling to eat enough nutrients, contact your prescriber.
Is it normal to feel full on small portions?
Yes, this is one of Mounjaro's main mechanisms. Feeling satisfied on smaller portions is the medication working as intended. Most people adapt to this within weeks. Ensure you're still getting adequate protein, vegetables, and nutrients despite eating less.
Can I use our GLP-1 weight loss calculator to estimate my calorie needs on Mounjaro?
Our GLP-1 weight loss calculator estimates projected weight loss at different doses based on clinical trial data — it can give you realistic expectations. For personalised calorie targets, always consult your GP or a registered dietitian, especially if you have underlying health conditions.
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.