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 you're taking Mounjaro (tirzepatide), your appetite naturally decreases, which often means you eat fewer calories without actively restricting food. However, there's no fixed calorie target that works for everyone — your individual needs depend on your current weight, height, activity level, and health goals. The NHS recommends working with a healthcare professional to establish a personalised nutrition plan that supports sustainable weight loss alongside your Mounjaro treatment. Our free GLP-1 weight loss calculator can help you estimate realistic projections based on your individual circumstances.
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.
Understanding Calorie Needs on Mounjaro Treatment
Mounjaro works by reducing appetite and helping you feel fuller after eating less — this is how the medication supports weight loss. Rather than following a strict calorie limit, most people on tirzepatide naturally consume fewer calories because the medication suppresses hunger hormones. The NHS recommends a calorie deficit of approximately 500 kcal per day to achieve sustainable weight loss of around 0.5 to 1 kg per week.
- Your daily calorie needs depend on your age, sex, current weight, height, and activity level
- The NHS suggests most women need 1,800–2,000 kcal per day and men need 2,200–2,600 kcal per day for weight maintenance
- For weight loss, a moderate deficit is safer than extreme restriction — aggressive calorie cutting can increase side effects and muscle loss
- Mounjaro is most effective when combined with reduced-calorie diet and increased physical activity
- A qualified prescriber or dietitian can assess your personal calorie needs during your clinical assessment for tirzepatide
Never follow extreme calorie restriction without medical guidance, especially when taking prescription weight loss medication.
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.
Practical Nutrition Approach While Taking Mounjaro
Rather than counting every calorie, focus on eating nutritious, protein-rich foods in smaller portions — this is often more sustainable on Mounjaro because the medication already suppresses hunger. Include vegetables, lean protein, whole grains, and healthy fats in meals you do eat. Drink plenty of water throughout the day, as dehydration can worsen nausea (a common side effect). Start with smaller meal portions and increase gradually if tolerated — many people find they naturally feel satisfied with less food. If you experience persistent nausea, indigestion, or constipation, speak to your GP or prescriber. Use our free progress tracker to monitor your weight loss alongside nutrition changes, helping you identify what works best for your body.
- 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.
Will Mounjaro automatically make me eat fewer calories?
Mounjaro reduces appetite by acting on hunger hormones, so most people naturally eat fewer calories without strict counting. However, it's not automatic — some individuals still need to be mindful of portion sizes. The medication supports reduced intake, but behaviour change and nutrition awareness still matter for best results.
Should I follow a very low-calorie diet while on Mounjaro?
No. The NHS recommends against very low-calorie diets (under 800 kcal daily) unless under close medical supervision. Combining Mounjaro with extreme calorie restriction increases side effects, muscle loss, and nutrient deficiency risk. A moderate deficit of 500 kcal per day is safer and more sustainable.
What if I'm not hungry on Mounjaro — should I still eat?
Yes. Even if you're not hungry, eat enough to meet your nutritional needs and prevent nutrient deficiencies. Mounjaro suppresses appetite, but you still need adequate protein, vitamins, and minerals. Eat smaller, nutrient-dense meals even if portions are small.
Can my GP tell me the exact calories I should eat on Mounjaro?
Your GP or a dietitian can give personalised calorie guidance during your clinical assessment and ongoing appointments. They'll consider your health, weight loss goals, and activity level. Use our free BMI calculator to check your current status, then discuss personalised nutrition with your healthcare team.
How do I know if my calorie intake is too low on Mounjaro?
Signs include persistent fatigue, dizziness, hair loss, or very gradual weight management (over 1.5 kg per week). Contact your GP immediately if you experience severe side effects. Most people on Mounjaro lose around 15–21% of body weight — if loss is much faster, medical review is recommended.
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.