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 Monjarro in the UK?
Monjarro is the UK brand name for tirzepatide, a prescription-only weight management injection licensed for use in the United Kingdom. It's a once-weekly injectable medicine that works differently from other weight loss treatments by activating two natural hormone pathways. This UK health guide explains how Monjarro works, who may be eligible, and how to access it through NHS or private routes. If you're exploring weight management options, understanding this medication 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 Monjarro Works and NHS Eligibility in the UK
Monjarro is a dual GIP and GLP-1 receptor agonist, which means it activates two separate hormone pathways that regulate appetite and blood sugar. This dual action helps reduce food cravings, supports feeling fuller after smaller meals, and may help regulate how your body uses fat. Unlike some weight loss medications, Monjarro is not insulin.
In the UK, NHS guidance indicates that Monjarro may be prescribed through specialist weight management services for adults with:
- A BMI of 30 kg/m² or above, OR
- A BMI of 27–29.9 kg/m² with weight-related health conditions (type 2 diabetes, prediabetes, high blood pressure, sleep apnoea, or cardiovascular disease)
- Lower thresholds may apply for South Asian, Chinese, Black African, or Black Caribbean adults due to higher health risks at lower BMI levels
Access to Monjarro in the UK varies significantly by region. Many NHS areas have extended waiting lists for specialist tier 3 weight management services, though NICE has approved tirzepatide for NHS use.
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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.
Accessing Monjarro and Managing Your Weight in the UK
In the UK, Monjarro is available through two main routes: NHS specialist weight management services (via GP referral) or private prescribing through online clinics. Clinical trials showed that participants lost an average of 15–21% of their body weight, though individual results vary significantly. Monjarro works best alongside a reduced-calorie diet and increased physical activity. Check your personal BMI using our free BMI calculator to understand your starting point. Your GP can advise whether Monjarro is suitable for you based on your individual health circumstances and whether you meet NHS eligibility criteria in your area.
- 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 Monjarro available on the NHS in the UK?
Yes, NICE has approved tirzepatide (Monjarro) for use within NHS specialist weight management services. However, access varies by region and waiting lists can be lengthy. You'll need a GP referral to a specialist tier 3 or tier 4 weight management service. Private prescribing is also available through regulated UK-licensed prescribers.
What is the difference between Monjarro and Wegovy?
Both are prescription-only weight loss injections, but Monjarro is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Monjarro has a higher starting dose and maximum dose. Clinical trial results suggest Monjarro may produce slightly higher average weight loss, though results vary individually.
How much weight can I expect to lose with Monjarro?
In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks at maximum dose, alongside a reduced-calorie diet and exercise. However, individual results vary significantly. Some people lose more, others less. Your GP or prescriber can discuss realistic expectations for you personally.
Who cannot take Monjarro in the UK?
Monjarro is not suitable for anyone under 18, pregnant or breastfeeding, or with a history of severe gastroparesis. It's also not recommended if you have a personal or family history of medullary thyroid cancer. Always inform your prescriber of all medical conditions and medications.
How do I check if I'm eligible for Monjarro in the UK?
Use our free BMI calculator to determine your BMI. If it's 30 or above, or 27–29.9 with weight-related conditions, you may be eligible. Book an appointment with your GP to discuss referral to specialist weight management services, or consult a regulated private prescriber for assessment.
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.