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 Should I Eat On Mounjaro?
When taking Mounjaro (tirzepatide), your daily calorie needs depend on your starting weight, activity level, and individual metabolism — not on the dose of the medication itself. Mounjaro works by reducing appetite and helping you feel fuller, meaning you may naturally eat fewer calories without strict restriction. However, a structured calorie target alongside the medication typically produces the best results. This guide explains how to determine your personal calorie needs while using this prescription-only 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.
Understanding Calorie Needs On Mounjaro
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that suppresses appetite and slows gastric emptying — how quickly food leaves your stomach. This means you'll likely eat less naturally without feeling deprived. However, medication alone doesn't clinically studied weight loss; a calorie deficit is still required.
A safe, sustainable approach is a deficit of around 500 kcal per day, which typically results in losing approximately 0.5 kg (1 lb) per week. For most UK adults, this means eating between 1,500–2,000 kcal daily, though your personal target depends on:
- Current body weight (heavier individuals have higher baseline calorie needs)
- Age and biological sex (younger adults and men typically need more)
- Activity level (sedentary vs. regular exercise)
- Metabolism (varies between individuals)
- Mounjaro dose (higher doses typically suppress appetite more)
Many users find that Mounjaro naturally reduces their appetite so significantly that they eat 1,200–1,500 kcal daily without hunger — but this should never be forced. If you're eating below 1,200 kcal consistently, discuss this with your GP or prescriber.
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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.
Calculating Your Personal Calorie Target
Use your current weight to estimate your Basal Metabolic Rate (BMR) — the calories your body burns at rest. A simple formula is: BMR = body weight (kg) × 24. For example, an 85 kg person burns approximately 2,040 kcal daily at rest.
Multiply your BMR by your activity factor: sedentary (1.2), lightly active (1.375), moderately active (1.55), or very active (1.725). This gives your Total Daily Energy Expenditure (TDEE). A 500 kcal deficit from this number is your target daily intake. Use our GLP-1 weight loss calculator to estimate potential weight loss at different calorie intakes and Mounjaro doses, and track your actual intake with our free progress tracker to monitor results over time.
- 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's the minimum calories I should eat on Mounjaro?
The NHS recommends not going below 1,200 kcal daily for women or 1,500 kcal for men without medical supervision. If Mounjaro suppresses your appetite so much that you're eating significantly less, discuss this with your GP — you may need to adjust your dose or add nutrient-dense foods. Never restrict calories extremely without professional guidance.
Does a higher Mounjaro dose mean I can eat fewer calories?
Not necessarily. While higher doses (up to 15 mg) typically suppress appetite more effectively, individual responses vary. The goal is sustainable weight loss through a moderate calorie deficit combined with medication, not extreme restriction. Your prescriber will assess what's safe for you based on your health history and metabolism.
How does Mounjaro affect hunger and calorie intake?
Mounjaro activates GIP and GLP-1 pathways in your brain, signalling fullness and reducing cravings. Most users report eating 30–50% less naturally within weeks. This is the medication's benefit — you should feel satisfied eating fewer calories, not deprived. If you're struggling with hunger despite Mounjaro, your dose may need adjustment.
Can I use a calorie calculator while on Mounjaro?
Yes — standard calorie calculators work well, but remember that appetite suppression from Mounjaro may lower your practical calorie needs below predictions. Track your actual intake and weight loss weekly, and adjust based on real results. Our free progress tracker helps log this alongside Mounjaro dose changes.
What if I'm losing weight too quickly on Mounjaro?
gradual weight management (over 1.5 kg per week) increases muscle loss risk and can cause nutritional deficiencies. If this happens, increase calories slightly or discuss dose adjustment with your prescriber. Aim for the NHS target of 0.5–1 kg per week for sustainable, healthy weight loss that preserves muscle mass.
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.