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
What Is Monjuaro? UK Health Information
Monjuaro (tirzepatide) is a prescription-only weight management injection licensed in the UK for adults living with obesity or overweight with weight-related health conditions. It works differently to other weight loss medications because it activates two natural hormone pathways — GIP and GLP-1 — which may help reduce appetite and support feeling fuller after smaller meals. This is UK health information to help you understand the medication; always consult your GP for personalised medical advice.
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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 Monjuaro Works and What to Expect
Monjuaro is a dual GIP and GLP-1 receptor agonist, which means it activates two hormone pathways in your body. This dual mechanism may help regulate appetite more effectively than single-action medications. When you eat, it supports your body's natural signals that help you feel satisfied, potentially reducing food cravings and the amount you eat at each meal. It also slows how quickly food leaves your stomach, though this effect typically reduces over time.
In clinical trials (SURMOUNT-1), adults taking Monjuaro alongside a reduced-calorie diet and increased physical activity experienced average weight loss of approximately 15–21% of their body weight, depending on the dose used. However, individual results vary significantly — some people lose more, others less. Weight loss is not assured. Monjuaro is injected once weekly under the skin, and doses are gradually increased from 2.5mg to a maximum of 15mg over several weeks. Your prescriber will assess whether this medication is right for you based on your individual health.
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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.
Eligibility, Side Effects, and NHS Access in the UK
You may be eligible for Monjuaro if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have lower BMI thresholds. Use our free BMI calculator to check your current BMI instantly.
Common side effects include nausea, diarrhoea, constipation, and stomach pain — these often improve as your body adjusts. In the NHS, Monjuaro is available through specialist tier 3 weight management services following referral from your GP; access varies by region and waiting lists can be long. Private access is available through online clinical assessments with UK-licensed prescribers.
Managing Monjuaro and Tracking ProgressMonjuaro requires careful storage in a refrigerator at 2–8°C unopened; after first use, pens can be kept at room temperature for up to 30 days. Inject once weekly into your stomach, thigh, or upper arm, rotating injection sites each week. If you miss a dose within 4 days, take it as soon as you remember; if more than 4 days have passed, skip that dose and continue your normal schedule. Never take a double dose.
For best results, combine Monjuaro with a balanced reduced-calorie diet and regular physical activity. Track your progress using our free progress tracker to monitor weight changes and see how you're progressing. Most people see meaningful weight changes within 4–8 weeks, though this varies. Always inform your prescriber of any medications you're taking, as Monjuaro may affect how some oral medicines are absorbed.
- 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.
Is Monjuaro the same as Wegovy or Ozempic?
No. Monjuaro (tirzepatide) is a dual GIP and GLP-1 medication made by Eli Lilly. Wegovy (semaglutide) is a single GLP-1 medication made by Novo Nordisk — both are licensed for weight management. Ozempic also contains semaglutide but is only licensed for type 2 diabetes, not weight loss. Monjuaro and Wegovy work differently and have different dose ranges and clinical trial results. Your prescriber will assess which is most suitable for you.
How quickly will I lose weight on Monjuaro?
Clinical trials showed average weight loss of 15–21% over 72 weeks alongside lifestyle changes — roughly 0.5–1 kg per week on average. However, individual results vary significantly. Some people lose weight faster, others more slowly. Weight loss is not assured. Combine Monjuaro with a reduced-calorie diet and increased physical activity for best results. Use our free weight loss calculator to estimate potential outcomes based on different doses.
What happens when I stop taking Monjuaro?
When you stop Monjuaro, the medication leaves your system over time and appetite regulation may return to normal. Some people maintain weight loss through continued diet and exercise changes; others may regain weight if lifestyle habits return to previous patterns. This is why combining the medication with sustainable dietary and activity changes is important. Your prescriber can advise you on a plan for stopping the medication safely.
Can I get Monjuaro on the NHS in the UK?
Yes, Monjuaro (tirzepatide) is approved by NICE for use within NHS specialist weight management services. However, access is limited to tier 3 services following GP referral, and waiting lists can be very long (months to years depending on your region). Private prescriptions are available more quickly through online clinical assessments. Eligibility requirements are the same either way — BMI 30+ or 27+ with weight-related health conditions.
What are the main side effects of Monjuaro?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — these often improve as your body adjusts. Other common effects include indigestion, injection site reactions, fatigue, and dizziness. Serious but rare side effects include severe stomach pain (possible pancreatitis) or gallbladder problems. Always report any concerning symptoms to your prescriber. Most side effects are manageable and temporary.
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.