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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Compound Mounjaro in the UK — What You Need to Know
Compound Mounjaro refers to tirzepatide prepared by compounding pharmacies rather than the licensed Mounjaro KwikPen manufactured by Eli Lilly. In the UK, this raises important questions about availability, cost, regulation, and safety. This guide explains what compound Mounjaro is, how it differs from licensed alternatives, and what you should consider before choosing this route for weight management. Always consult your GP or a licensed prescriber before starting any weight loss medication.
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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.
What Is Compound Mounjaro and How Does It Compare to Licensed Mounjaro?
Compound Mounjaro is tirzepatide prepared by a compounding pharmacy — a facility licensed to mix medications according to a prescription but operating outside the standard pharmaceutical manufacturing process. The licensed version, Mounjaro KwikPen, is manufactured by Eli Lilly under strict MHRA quality controls and is approved for weight management in UK adults.
Key differences include:
- Quality assurance: Licensed Mounjaro undergoes rigorous MHRA testing; compounds are less regulated
- Consistency: Licensed versions have assured dose accuracy; compound batches may vary
- Sterility: Licensed Mounjaro has verified sterility standards; compounds depend on pharmacy standards
- Availability: Licensed Mounjaro is available through NHS specialist services and private prescribers; compounds are sourced through private channels only
- Cost: Compounds may be cheaper initially but carry higher risk
The MHRA has raised safety concerns about unregulated compound medications. Licensed tirzepatide (Mounjaro KwikPen) remains the safest, verified option available in the UK.
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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 vs Private Access to Licensed Tirzepatide in the UK
NHS route: Tirzepatide (Mounjaro) is available through NICE-approved specialist weight management services. Access requires GP referral to a tier 3 or tier 4 service. Waiting times vary significantly by region—some areas have waiting lists of 6–18 months. Once approved, tirzepatide is provided at no cost to eligible patients.
Private route: Licensed Mounjaro KwikPen is available through private prescribers and registered pharmacies. An online clinical assessment typically costs £20–£50, and medication costs approximately £130–£320 per month depending on dose. This provides faster access without NHS waiting lists but requires private payment. Both routes provide verified, MHRA-regulated tirzepatide—not compounds. Use our free GLP-1 weight loss calculator to estimate potential outcomes with licensed tirzepatide at different doses.
NHS route: Tirzepatide (Mounjaro) is available through NICE-approved specialist weight management services accessed via GP referral to tier 3 or tier 4 services. Waiting times vary significantly by region—some areas have waiting lists of 6–18 months. Once approved, tirzepatide is provided at no cost to eligible patients.
Private route: Licensed Mounjaro KwikPen is available through private prescribers and registered pharmacies following online clinical assessment (typically £20–£50). Medication costs approximately £130–£320 per month depending on dose. This provides faster access without NHS waiting lists. Both routes provide verified, MHRA-regulated tirzepatide. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses.
- 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 compound Mounjaro legal in the UK?
Compounding pharmacies are licensed in the UK, but their products are less regulated than licensed medications like Mounjaro KwikPen. The MHRA has raised safety concerns about compound tirzepatide, particularly regarding sterility, dose accuracy, and contamination risk. While obtaining a compound may not be illegal, it carries higher health risks than licensed alternatives.
Why would someone choose compound Mounjaro over licensed Mounjaro KwikPen?
The main reason is often cost—compounds may initially appear cheaper. However, this does not account for quality risks, potential ineffectiveness, and health complications. Licensed tirzepatide (Mounjaro KwikPen) is available privately at £130–£320 monthly, and through NHS specialist services at no cost if eligible.
What are the specific risks of compound tirzepatide?
Risks include inconsistent dosing, contamination, lack of sterility verification, and unknown storage conditions. Additionally, compound batches lack the rigorous testing undergone by licensed Mounjaro. If complications occur, medical professionals may struggle to identify the cause or provide appropriate treatment.
How does Mounjaro compare to Wegovy for weight management?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are licensed GLP-1-based injections approved in the UK. Mounjaro uses a dual GIP+GLP-1 mechanism and may produce slightly larger average weight loss. Wegovy is a GLP-1-only injection. Both require prescription and clinical assessment. Licensed versions of either are safer than compounds.
Can my GP prescribe licensed Mounjaro privately?
Yes. Your GP can issue a private prescription for licensed Mounjaro KwikPen if they assess you as eligible. You then take this to a registered UK pharmacy. Alternatively, private weight management services offer online consultations with licensed prescribers who can assess and prescribe Mounjaro KwikPen for you directly.
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.