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 Monjarno and How Does It Work?
If you've searched for "Monjarno" as a weight loss option, you may be thinking of tirzepatide (Mounjaro) or semaglutide (Wegovy) — the two main GLP-1 and GIP receptor agonist injections licensed for weight management in the UK. These are prescription-only medicines that may help support weight loss alongside a reduced-calorie diet and increased physical activity. This UK health guide explains how these medications work, who may be eligible, and how to access them through NHS health services or private prescribing. Individual results vary, and a clinical assessment from a qualified healthcare professional is always required before prescription.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 GLP-1 Weight Loss Medications Work
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways in your body. GLP-1 is a hormone that signals fullness to your brain, slows stomach emptying, and helps regulate appetite. GIP (glucose-dependent insulinotropic polypeptide) works alongside GLP-1 to amplify these effects. Together, they may help reduce cravings, support feeling fuller after smaller meals, and assist with sustainable weight management.
Wegovy (semaglutide) is a GLP-1 agonist only — activating a single hormone pathway. Clinical trials (STEP-1) showed an average weight loss of approximately 15% of body weight over 68 weeks, though individual results vary significantly.
Both medications are prescription-only and require a clinical assessment to determine suitability. They are not insulin and work through appetite regulation rather than blood sugar control alone.
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.
UK Eligibility and How to Access Weight Loss Treatment
In the UK, adults with a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea), may be eligible for prescription weight loss medications. Access is available through two routes:
- NHS route: Referral to a tier 3 specialist weight management service via your GP. Availability and waiting times vary significantly by region.
- Private route: Online consultation with a UK-licensed prescriber, followed by prescription from a GPhC-registered pharmacy if clinically appropriate.
Use our free BMI calculator above to check your personal BMI and determine whether you may fall within the eligible range. Your GP or a licensed prescriber can then assess your individual health circumstances and discuss the most appropriate option.
Weight loss medications are most effective when combined with lifestyle changes — a reduced-calorie diet and regular physical activity. Track your progress with our free progress tracker to monitor your weight loss journey over time. Remember that individual results vary, and prescription medications work best as part of a comprehensive health plan, not as a standalone solution.
- 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 Monjarno the same as Mounjaro?
"Monjarno" doesn't appear to be an official medication name. You may be referring to Mounjaro (tirzepatide) or Wegovy (semaglutide) — both are GLP-1 receptor agonist injections licensed for weight management in the UK. If you've encountered this term, it's worth double-checking the exact medication name with your prescriber or pharmacist.
Are these weight loss injections available on the NHS?
Yes, tirzepatide (Mounjaro) and semaglutide (Wegovy) are available through NHS specialist weight management services. Access requires referral from your GP to a tier 3 service. However, availability and waiting times vary significantly by region. Private access is also available through online prescribing.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Wegovy is licensed specifically for weight management (up to 2.4 mg), whilst Ozempic is licensed for type 2 diabetes (up to 2 mg). Ozempic is not approved for weight loss in the UK. Always use the medication prescribed by your healthcare professional.
How much weight can I expect to lose?
Clinical trials showed average weight loss of approximately 15–21% of body weight, but individual results vary significantly depending on diet, exercise, dose, and personal factors. Our GLP-1 weight loss calculator can help project potential outcomes at different doses. Always discuss realistic expectations with your prescriber.
Are weight loss injections suitable for everyone?
No. These medications are prescription-only and require clinical assessment. They're not suitable for pregnant women, those under 18, or people with certain medical conditions. Your GP or prescriber will evaluate your health history, medications, and suitability before prescription. Always declare all existing health conditions and medications.
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.