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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What Is Monjoro? UK Weight Management Guide
Monjoro is the brand name for tirzepatide, a prescription-only weight management injection licensed in the UK. You may have heard it called "Monjaro" — both refer to the same medication made by Eli Lilly. This guide explains how Monjoro works, who can access it on the NHS or privately, what to expect from treatment, and how it compares to other weight loss options. If you're considering weight management support, understanding the facts about prescription medications is an important first step.
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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 Monjoro Works and What Makes It Different
Monjoro is a dual GIP and GLP-1 receptor agonist — this dual mechanism is what sets it apart from other weight loss injections like Wegovy (which is GLP-1 only). GIP and GLP-1 are natural hormones your body produces after eating. Monjoro mimics and enhances both signals, which may help regulate appetite, reduce food cravings, and support feeling fuller after smaller meals. The medication also slows how quickly food leaves your stomach, though this effect typically reduces over time. You can calculate your potential weight loss using our free GLP-1 weight loss calculator, which shows projected results at different doses based on clinical trial data. It's important to note that Monjoro is not insulin — it works differently from diabetes medications, though it can help improve blood sugar control as a side effect of weight loss. Clinical trials (SURMOUNT-1) showed that at maximum dose (15 mg weekly), participants lost an average of approximately 21% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly.
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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, Doses, and What to Expect
In the UK, Monjoro may be prescribed if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds due to higher health risks at these levels. Check your personal BMI using our free BMI calculator to understand where you stand. Monjoro starts at 2.5 mg weekly, increasing gradually over 20 weeks to a maximum of 15 mg. Each dose is a once-weekly injection you can self-administer at home. NHS access is through specialist tier 3 weight management services (often with waiting lists), while private access is available through online prescribers following clinical assessment. Common side effects include nausea, diarrhoea, and stomach discomfort — these often improve as your body adjusts. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and allergic reactions, which require immediate medical attention.
- 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 Monjoro the same as Monjaro?
Yes. Monjoro and Monjaro are the same medication — tirzepatide made by Eli Lilly. Both names are used in the UK. The branded spelling varies, but they contain identical active ingredients and work the same way.
Can I get Monjoro on the NHS in the UK?
Yes, Monjoro (tirzepatide) is approved by NICE for NHS specialist weight management services. However, access requires referral to a tier 3 or tier 4 service through your GP, and availability varies significantly by region. Waiting lists can be several months to over a year in many areas.
How much weight will I lose on Monjoro?
Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks at different doses, alongside diet and exercise. However, individual results vary considerably — some people lose more, some less. A prescriber can discuss realistic expectations based on your circumstances.
What are the main side effects of Monjoro?
Very common side effects include nausea, diarrhoea, vomiting, and stomach pain. Most improve within the first few weeks as your body adjusts. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and allergic reactions — seek urgent medical attention if these occur.
How does Monjoro compare to Wegovy for weight loss?
Both are licensed weight loss injections in the UK. Monjoro uses dual GIP+GLP-1 mechanism and showed slightly higher average weight loss (21% vs 15% at maximum doses in trials). Wegovy is GLP-1 only. Both require prescription, regular injections, and lifestyle changes. A prescriber can advise which suits you better.
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.