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 While Taking Mounjaro?
There's no single "correct" calorie intake for everyone on Mounjaro — it depends on your starting weight, metabolism, activity level, and which dose you're taking. The NHS recommends creating a moderate calorie deficit (typically 500 kcal below your daily needs) to lose around 0.5–1 kg per week. Mounjaro works best when combined with reduced-calorie eating and increased physical activity. Your prescriber or a registered dietitian can assess your individual needs and help you set a realistic calorie target based on your health goals.
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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.
Calorie Intake and Mounjaro: NHS and Clinical Evidence
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that helps reduce appetite and support fullness after smaller meals. It's not a replacement for dietary changes — the medication works most effectively alongside a reduced-calorie diet. In the SURMOUNT clinical trials, participants achieved weight loss of 15–21% body weight on average, but this was always combined with calorie reduction and increased physical activity.
General NHS guidance for calorie intake:
- Most adults need 500 kcal daily deficit to lose approximately 0.5 kg per week
- Very low calorie diets (under 800 kcal/day) should only be followed under medical supervision
- A balanced, sustainable approach (1200–1800 kcal/day for most adults) is recommended
- Your GP or registered dietitian can calculate your personalised calorie target based on your current weight, activity level, and health status
Starting Mounjaro typically reduces hunger and cravings, which naturally makes eating fewer calories easier. However, individual response varies significantly.
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 Guidance While on Mounjaro
Rather than focusing solely on calorie counting, the NHS recommends a balanced approach: prioritise protein (supports fullness and muscle retention), include plenty of vegetables, choose whole grains, and drink adequate water. Mounjaro may slow gastric emptying, so some people find they need to eat smaller, more frequent meals to avoid discomfort. Common side effects like nausea and reduced appetite are normal — if you're struggling to eat enough to meet basic nutritional needs, contact your prescriber immediately.
Track your progress using realistic markers: weight loss, how you feel, energy levels, and how your clothes fit. Our free progress tracker can help you log changes over time. Your GP can also request blood tests to monitor your health while on Mounjaro, particularly if you have type 2 diabetes or other health conditions.
- 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 average calorie intake while on Mounjaro?
There's no single target — it depends on your individual needs. Most people create a 500 kcal daily deficit below their maintenance needs. The NHS recommends losing no more than 0.5–1 kg per week. Your prescriber can help you set a personalised target based on your current weight, height, activity level, and any health conditions.
Does Mounjaro mean I don't need to reduce calories?
No. Mounjaro supports weight loss by reducing appetite and cravings, but it's not a replacement for dietary changes. Clinical trials show weight loss only occurs when Mounjaro is combined with a reduced-calorie diet and increased physical activity. The medication makes calorie reduction easier to sustain, not automatic.
Can I eat normally while taking Mounjaro?
Some people find they naturally eat less because Mounjaro reduces hunger. However, "normal" eating patterns may have contributed to weight gain initially. You'll likely need to make conscious dietary changes — focusing on balanced nutrition, portion control, and regular meals rather than restrictive dieting. Your GP can refer you to a registered dietitian for personalised support.
What if I can't eat enough calories on Mounjaro?
If you're struggling to meet basic nutritional needs or experiencing severe loss of appetite, contact your prescriber immediately. This may indicate your dose is too high or that the medication isn't suitable for you. Never skip meals or eat below 1200 kcal daily without medical supervision, as this can cause nutrient deficiencies and muscle loss.
Should I count calories strictly while on Mounjaro?
Strict calorie counting works for some people, but others find mindful eating more sustainable — focusing on fullness cues, balanced meals, and avoiding ultra-processed foods. Both approaches can be effective. The key is finding an approach you can maintain long-term alongside your Mounjaro treatment.
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.