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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What Does Mounjaro Do — How It Works and UK Access
Mounjaro (tirzepatide) is a prescription-only weekly injection that may help with weight management in UK adults. It works as a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways to help reduce appetite and support feeling fuller after meals. Many people ask what Mounjaro actually does and how to access it in the UK. This guide explains how the medication works, the cost differences between NHS and private routes, and what to expect when seeking a prescription. Whether you're exploring this option through your GP or privately, understanding how Mounjaro functions and the practical access routes is essential for making an informed decision.
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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 Much Does Mounjaro Cost in the UK?
Mounjaro costs vary significantly depending on whether you access it through the NHS or privately. Through the NHS specialist weight management services, the medication is provided free at the point of use — though access is limited and availability varies by region. Most NHS areas have long waiting lists (sometimes 12–24 months or longer) because specialist tier 3 and tier 4 weight management services have restricted capacity.
Through private prescribing, Mounjaro typically costs between £150–£320 per month depending on your dose and the prescribing provider. Lower doses (2.5–5 mg) cost less, while higher maintenance doses (10–15 mg) cost more. Each KwikPen contains four weekly injections, so you'll need one pen per month. Private prescriptions require an online clinical assessment with a UK-licensed prescriber, and the prescription must be dispensed by a GPhC-registered pharmacy. Many people choose private access to avoid NHS waiting lists, though this requires upfront payment.
- NHS route: free but long waiting lists, regional variation
- Private route: £150–£320/month, faster access, requires clinical assessment
- Both routes require a prescription from a licensed prescriber
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 — Which Route Is Right for You?
The NHS route is ideal if you're willing to wait and have been referred to a specialist weight management service by your GP. Tier 3 services offer specialist support, monitoring, and diet advice — though waiting lists are currently very long in many areas. The NHS prescribes Mounjaro free, but you'll need a BMI of 30 or above (or 27–29.9 with weight-related health conditions like type 2 diabetes or cardiovascular disease) and may require additional assessments.
The private route is faster: book an online consultation, answer health questions, and if approved by a UK-licensed prescriber, receive your prescription within days. You then pay for the medication directly. This route is suitable if you want to start quickly without waiting lists. Both routes are legitimate — your choice depends on timeframe, budget, and preference for specialist NHS support versus faster private access.
- NHS: free, specialist support, long waits, regional variation
- Private: £150–£320/month, no waiting lists, faster access, self-funded
- 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.
What exactly does Mounjaro do in your body?
Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist. It works by activating two natural hormone pathways in your gut, which signals to your brain that you're full, reduces cravings, and slows how quickly food leaves your stomach. This may help you eat smaller portions and feel satisfied with less food.
How long does Mounjaro take to work?
Most people notice changes in appetite within the first 1–2 weeks of starting Mounjaro. Weight loss typically becomes measurable within 4–8 weeks, though individual results vary. Clinical trials showed average weight loss of 15–21% over 72 weeks when used alongside diet and exercise.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is approved by NICE for NHS use in specialist tier 3 weight management services. However, access is limited by waiting lists and regional availability. Your GP can refer you to your local specialist service, but waiting times are often 12+ months in many areas.
How much does a Mounjaro prescription cost privately?
Private Mounjaro prescriptions typically cost £150–£320 per month depending on your dose. You'll need one KwikPen per month (four weekly injections). This requires an online consultation with a UK-licensed prescriber and payment to a private pharmacy — but access is usually available within days.
Do I need to use our GLP-1 calculator to see if Mounjaro is right for me?
Our GLP-1 weight loss calculator can help you estimate potential weight loss at different Mounjaro doses based on your current weight — though it's not a substitute for a clinical assessment. A UK-licensed prescriber will ultimately assess whether Mounjaro is suitable for your individual health needs. ```
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.