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
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Mounjoro — Complete UK Health Information
Mounjoro (tirzepatide) is a prescription-only weight management injection licensed in the UK for adults with excess weight and related health conditions. This comprehensive UK health guide explains how Mounjoro works, who may be eligible, what to expect, and how to access it through the NHS or private prescribing. Individual results vary, and Mounjaro is always used alongside lifestyle changes including diet and physical activity. Your GP can advise whether this medication may be suitable for your personal health situation.
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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 Mounjoro Works and UK Eligibility
Mounjoro is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways in the body. This dual mechanism may help reduce appetite, support feeling fuller after meals, and assist with weight management when combined with a reduced-calorie diet and increased physical activity.
According to NHS guidance, Mounjoro may be prescribed to adults in the UK who have:
- A BMI of 30 kg/m² or above, OR
- A BMI of 27–29.9 kg/m² with at least one weight-related health condition (such as type 2 diabetes, prediabetes, high blood pressure, or obstructive sleep apnoea)
- Lower eligibility thresholds may apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage
NHS access is through specialist tier 3 weight management services — your GP can refer you. Private access is available through online clinical assessment with a UK-licensed 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.
Side Effects, Dosing, and NHS Resources
Common side effects reported in clinical trials include nausea, diarrhoea, vomiting, and constipation — these often improve over time as the body adjusts. Serious side effects are rare but may include severe stomach pain (possible pancreatitis) or gallbladder problems; seek immediate medical attention if you experience these.
Mounjoro dosing starts at 2.5 mg per week and increases gradually up to a maximum of 15 mg per week, based on individual tolerance and response. Each dose is a once-weekly injection. Calculate your personal BMI using our free BMI calculator above to understand where your weight sits according to NHS guidelines. Your GP or a licensed prescriber can assess your eligibility and discuss whether Mounjoro is appropriate for your individual circumstances and health history.
- 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 difference between Mounjoro and Wegovy?
Both are prescription weight management injections licensed in the UK. Mounjoro (tirzepatide) uses a dual GIP+GLP-1 mechanism, whilst Wegovy (semaglutide) uses a single GLP-1 mechanism. Clinical trials showed different average weight loss outcomes, but individual results vary significantly. A prescriber can help you understand which may be more suitable for you.
How do I access Mounjoro on the NHS in the UK?
NHS access is through specialist tier 3 weight management services. Ask your GP for a referral to your local specialist weight management service. Waiting times vary by region. Private access is available through online consultation with a UK-licensed prescriber without an NHS referral, though this involves a cost.
Can I use our weight converter to check if I'm eligible for Mounjoro?
Use the weight converter on this page to check your weight in kg and stone. Then calculate your BMI using our free BMI calculator to see where you fall according to NHS guidelines. However, only a healthcare professional can assess your full eligibility based on your individual health, medical history, and weight-related conditions.
What happens if I miss a dose of Mounjoro?
If you miss a dose, take it within 4 days and resume your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next dose on the scheduled day — never take a double dose. Always follow your prescriber's specific guidance.
Will I lose weight assured with Mounjoro?
Weight loss is not assured and results vary between individuals. Clinical trials showed average weight loss of 15–21% of body weight at higher doses, but this was achieved alongside reduced-calorie diet and increased physical activity. Your GP or prescriber can discuss realistic expectations based on your personal health situation.
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.