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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Mounjaro Fat Jab — UK Cost, Access & How to Get It
Mounjaro, commonly called a "fat jab" in the UK, is a prescription-only weight management injection containing tirzepatide. Access and cost vary significantly depending on whether you pursue NHS specialist services or private prescription routes. Understanding your options, eligibility requirements, and realistic costs will help you make an informed decision about whether this treatment is right for you.
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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.
Private Mounjaro Cost in the UK
Private prescription costs for Mounjaro vary across GPhC-registered online pharmacies, typically ranging from £129 to £320 per month depending on your dose. Starting doses (2.5 mg) are usually at the lower end; maximum doses (15 mg) at the higher end. You pay per pen, and each KwikPen contains 4 weeks of doses.
- 2.5 mg dose: approximately £129–£160/month
- 5–7.5 mg dose: approximately £160–£220/month
- 10–15 mg dose: approximately £220–£320/month
Many private providers offer repeat prescription discounts or subscription options. Online consultations typically cost £20–£50 and are often waived if you proceed with treatment. Always compare providers and ask about delivery costs, which may add £5–£15 per order.
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 Routes
NHS route: Free on prescription if prescribed through a tier 3 specialist weight management service, but requires GP referral and assessment. Waiting lists vary dramatically by region—some areas have waits of 12–24 months. Availability depends on your integrated care board (ICB) commissioning decisions.
Private route: Available immediately through online prescribers following a clinical assessment questionnaire. No NHS referral needed. You pay for consultations and medication. This route is faster but involves out-of-pocket costs. Both routes require a UK-licensed prescriber to assess your eligibility based on BMI and health history.
Use our free BMI calculator above to check your eligibility threshold (BMI 30 or above, or 27 with weight-related health conditions). Our GLP-1 weight loss calculator can help you project potential outcomes at different doses, supporting your cost-benefit analysis.
- 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 much does Mounjaro cost on the NHS?
Mounjaro is free on NHS prescription if prescribed through a specialist tier 3 weight management service. You only pay standard prescription charges (£9.90 per item in England, 2024). However, accessing NHS treatment requires GP referral and assessment, with waiting lists often exceeding 12 months depending on your region.
Can I get Mounjaro privately without seeing my GP?
Yes. Private online prescribers can assess you directly following a clinical questionnaire without an NHS referral. You must have a UK address and be registered with a GP (for safety), but you do not need their permission. Private prescription, assessment, and medication are all out-of-pocket costs.
What happens if I can't afford the private cost?
Explore NHS routes—ask your GP about tier 3 referral even with waiting lists. Some integrated care boards fund Mounjaro access based on BMI and comorbidities. You could also investigate lower-cost alternatives like Saxenda (liraglutide), which is sometimes available. Discuss realistic timescales and costs with your GP.
How long does a private Mounjaro prescription take to arrive?
Once approved by a prescriber, most GPhC-registered providers deliver within 3–7 working days. Initial consultations can be completed online and approved within 24–48 hours. NHS route is significantly slower due to referral and assessment waiting lists, which can be months.
Will my private Mounjaro prescription be recognised by the NHS if I switch?
Your private prescription is a valid NHS prescription in terms of the medicine itself, but the NHS will not fund continuation if you switch routes. You would need to be assessed separately for NHS specialist services. Any Mounjaro you obtain privately remains your responsibility; NHS funding does not backdate.
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.