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 a GLP-1 Medication? What UK Patients Need to Know
Mounjaro (tirzepatide) is not technically a GLP-1 medication — it's actually a dual GIP and GLP-1 receptor agonist, which makes it different from other weight loss injections available in the UK. This means Mounjaro activates two separate hormone pathways rather than one, which may explain why clinical trials showed slightly higher average weight loss compared to traditional GLP-1 medicines like Wegovy. Understanding this distinction matters when discussing eligibility and NHS prescribing with your GP. If you're considering weight management treatment in the UK, our free GLP-1 weight loss calculator can help you explore potential outcomes at different doses.
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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.
How Mounjaro Differs From GLP-1 Medications
Mounjaro's dual mechanism sets it apart from single-pathway GLP-1 agonists. While GLP-1 medications like Wegovy activate only the glucagon-like peptide-1 pathway, Mounjaro activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors simultaneously. This dual action may help regulate appetite more effectively and support fat utilisation in the body.
In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight depending on dose, whilst traditional GLP-1 medicines showed average losses around 14–15%. Both are prescription-only weight loss injections available in the UK through NHS specialist services or private prescribing, delivered as a once-weekly injection via KwikPen. The key difference is mechanism, not efficacy — individual results vary considerably, and the "best" medication depends on personal health profile and GP assessment rather than mechanism alone.
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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.
NHS Prescribing of Mounjaro and GLP-1 Alternatives in the UK
The NHS has approved Mounjaro (tirzepatide) and Wegovy (semaglutide, a traditional GLP-1) for weight management through specialist tier 3 services, based on NICE guidance. Eligibility depends on BMI and weight-related health conditions rather than which medication class you qualify for. Adults with a BMI of 30 or above, or 27–29.9 with conditions like type 2 diabetes or hypertension, may be eligible.
Access varies significantly by region and NHS waiting lists can be lengthy. Many patients now access Mounjaro or Wegovy privately through online prescribing services following a clinical assessment. Both require a prescription from a UK-licensed prescriber before dispensing by a registered pharmacy. Use our free BMI calculator to check your starting point, then discuss prescription options with your GP or a licensed prescriber.
- 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 Mounjaro a GLP-1 or something else?
Mounjaro is a dual GIP and GLP-1 receptor agonist, not a traditional GLP-1 medication. It activates two hormone pathways instead of one. Wegovy is a true GLP-1 agonist. Both are prescription-only weight management injections in the UK, but Mounjaro's dual mechanism may produce slightly different results in clinical trials.
Does Mounjaro work better than GLP-1 medications like Wegovy?
Clinical trial data suggests Mounjaro produced marginally higher average weight loss (15–21%) compared to GLP-1 medications like Wegovy (around 14–15%), but individual results vary significantly. Neither is universally "better" — the right choice depends on your health profile, side effect tolerance, and GP assessment.
How do I access Mounjaro in the UK through the NHS?
Mounjaro is available through NHS specialist tier 3 weight management services, typically via GP referral. NICE has approved it for eligible adults. However, NHS availability and waiting times vary greatly by region (ICB). Many people access it faster through private online prescribing following a clinical assessment.
What's the difference between Mounjaro and Wegovy prescribing in the UK?
Both require UK GP prescription and clinical assessment. Mounjaro is a dual agonist; Wegovy is a traditional GLP-1 agonist. Both are once-weekly injections. NHS access is through specialist services for both; private access is available from registered online prescribers for either medication.
Can my GP prescribe Mounjaro directly, or do I need a specialist?
NHS Mounjaro prescribing typically comes through specialist tier 3 services rather than primary care GPs, though this varies regionally. Private prescribers (after online assessment) can issue prescriptions outside the NHS pathway. Always consult your GP first about available options in your area.
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.