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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Is Mounjaro Good for Weight Loss in the UK?
Whether Mounjaro is "good" for you depends on your individual circumstances, health profile, and what you're trying to achieve. Mounjaro (tirzepatide) is a prescription-only GLP-1/GIP receptor agonist approved by the MHRA and supported by NICE guidance for weight management in UK adults. Clinical trials showed it can help people lose an average of 15–21% of their body weight, but results vary significantly. This guide explains how Mounjaro works in the UK context, who may benefit, and how to access it through the NHS or privately.
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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.
NHS Eligibility and Evidence for Mounjaro in the UK
In the UK, Mounjaro is prescribed through NHS specialist tier 3 weight management services or privately following a clinical assessment. NHS eligibility criteria include:
- BMI of 30 kg/m² or above (obesity), OR
- BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea
- Lower thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults due to higher metabolic risk
The SURMOUNT-1 clinical trial demonstrated that tirzepatide at maximum dose (15 mg) achieved average weight loss of approximately 20.9% of body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly — some people lost 10%, others over 25%. Mounjaro works by activating two natural hormone pathways (GIP and GLP-1), which helps regulate appetite, reduce cravings, and support feeling fuller after smaller meals. Use our free BMI calculator above to check whether you might meet eligibility criteria, and our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
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.
NHS vs Private Access: How to Get Mounjaro in the UK
NHS route: Referral from your GP to a specialist tier 3 weight management service is required. NICE has approved tirzepatide for NHS use, but availability and waiting times vary significantly by region (ICB area). Some areas have waiting lists of many months or years. Private route: Available through GPhC-registered online clinics following an online clinical assessment with a UK-licensed prescriber. No NHS referral needed. Costs typically range from £129–£320 per month depending on dose. Both routes require a clinical assessment to confirm suitability — Mounjaro is not appropriate for everyone, particularly those with a personal or family history of thyroid cancer, or those pregnant or planning pregnancy. Your GP can advise which route is most appropriate for you and help you access support alongside medication.
- 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.
How does Mounjaro compare to Wegovy for UK weight loss?
Both are GLP-1-based injections licensed in the UK for weight management. Mounjaro (tirzepatide) uses dual GIP+GLP-1 activation and showed slightly higher average weight loss (20.9% at 15 mg) compared to Wegovy (semaglutide, single GLP-1, approximately 15% average loss). However, individual results vary greatly — the "best" option depends on your health profile, medical history, and clinical assessment. A prescriber will advise which is more suitable for you.
What side effects should I expect from Mounjaro?
Very common side effects include nausea, diarrhoea, vomiting, and stomach pain—usually temporary and often improve as your body adjusts. Common side effects include indigestion, headache, fatigue, and injection site reactions. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and allergic reactions. Always report any concerning symptoms to your prescriber immediately. Side effects typically reduce with time at the same dose.
Is Mounjaro available on the NHS in my area?
Mounjaro is approved by NICE for NHS use, but availability varies significantly by region. Some ICBs (Integrated Care Boards) have robust specialist weight management services; others have limited provision. Contact your GP to ask about NHS specialist services in your area. If waiting times are long or services unavailable, private options are available without requiring NHS referral, though these involve private costs.
How long does Mounjaro take to work?
Weight loss typically begins within the first 2–4 weeks on a dose, though some people notice appetite reduction sooner. Maximum benefit at each dose level is usually seen around 4–8 weeks. Mounjaro requires dose titration — you start at 2.5 mg weekly and increase gradually up to 15 mg over approximately 4–5 months. Patience is important; sustainable weight loss builds gradually alongside dietary changes and increased physical activity.
Can I use our tools to help track Mounjaro progress?
Yes. Use our free weight converter to track your weight in the units you prefer (kg, stone, lbs), our BMI calculator to monitor changes in your BMI as you progress, and our progress tracker to log weekly or monthly weight changes. Seeing your progress tracked over weeks and months can be motivating and helpful for conversations with your healthcare team about whether dose adjustments are needed.
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.