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 You Eat on Mounjaro?
When taking Mounjaro (tirzepatide) for weight management, calorie intake naturally decreases because the medication suppresses appetite and helps you feel fuller after smaller meals. Most people on Mounjaro eat between 1,200–1,800 calories daily without deliberately restricting, as the appetite-suppressing effects of the dual GIP and GLP-1 mechanism make overeating uncomfortable. However, calorie needs vary by individual, and your GP or prescriber can advise what's appropriate for your personal situation. Try our GLP-1 weight loss calculator to explore potential outcomes at different doses.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Mounjaro vs Wegovy: Calorie Requirements and Appetite Suppression
Mounjaro (tirzepatide) activates both GIP and GLP-1 receptors, creating a dual appetite-suppression effect. Clinical trials (SURMOUNT-1) showed participants naturally reduced calorie intake without strict dieting — most consumed 1,200–1,600 calories daily on higher doses. The medication slows gastric emptying, meaning food stays in your stomach longer, creating prolonged satiety.
Wegovy (semaglutide) works as a GLP-1-only agonist, producing similar but typically slightly less intense appetite suppression. STEP trial data showed participants naturally ate fewer calories, averaging around 1,300–1,700 daily depending on dose. Both medications require a reduced-calorie diet to work effectively — they support appetite control but do not replace dietary changes.
- Mounjaro: dual mechanism may suppress appetite more intensely
- Wegovy: single mechanism, slightly milder appetite reduction on average
- Both: calorie deficit still essential for weight loss
- Individual response varies significantly between people
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.
Finding Your Right Calorie Intake: Prescriber Guidance and Individual Needs
Your prescriber or GP should assess your individual calorie needs based on your age, sex, activity level, current weight, and any medical conditions. A balanced approach combines the appetite suppression provided by Mounjaro or Wegovy with a sustainable, nutritious diet — typically 500 kcal below your daily requirement for steady weight loss of 0.5–1 kg weekly.
Do not aim to eat as little as possible; insufficient calories can lead to muscle loss, nutrient deficiencies, and fatigue. Track your energy levels and hunger cues while on the medication. Use our progress tracker to monitor your weight loss and adjust your diet if you feel unwell. If you experience persistent nausea, vomiting, or inability to eat, contact your prescriber immediately — this may require a dose adjustment or assessment.
- 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.
How many calories can I eat safely while on Mounjaro?
Safe calorie intake depends on your personal factors (age, sex, activity level, starting weight). NHS guidance suggests a deficit of around 500 kcal daily for sustainable weight loss of 0.5–1 kg per week. Most people on Mounjaro naturally consume 1,200–1,800 calories without restriction due to appetite suppression. Your GP can advise your specific target.
Is Mounjaro or Wegovy better for calorie restriction?
Mounjaro's dual GIP+GLP-1 mechanism may produce slightly stronger appetite suppression than Wegovy's single GLP-1 action. Clinical trials (SURMOUNT vs STEP) showed similar average calorie intake reduction with both medications. Individual response varies — what works best depends on your personal physiology and prescriber assessment, not the medication alone.
What if I can't eat enough calories while on Mounjaro?
If eating feels impossible or you experience severe nausea and vomiting, contact your prescriber immediately. This is not normal and may indicate your dose is too high for you. Your prescriber can reduce your dose or adjust your treatment plan. Do not try to force eating if genuinely unable — this requires medical guidance.
Do I need to count calories while on Mounjaro or Wegovy?
Formal calorie counting is not always necessary — many people find the appetite suppression naturally leads to appropriate intake. However, tracking food intake loosely helps ensure you're eating enough nutrients and not accidentally undereating. A balanced diet with protein, vegetables, and whole grains is more important than hitting exact calorie numbers.
Can I eat normally while on Mounjaro compared to before?
No — both Mounjaro and Wegovy are designed to reduce your appetite so you eat less than you did before. This is how they support weight loss. Portion sizes typically reduce by 30–50% due to earlier fullness. This is expected and desired, as long as you're eating nutritious food in adequate amounts. Use our BMI calculator to track how your weight changes as your intake naturally adjusts.
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.