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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Fat Jab Cost in the UK — What You Need to Know
If you're researching fat jabs cost in the UK, you're likely considering weight loss injections as part of your health plan. The term "fat jabs" colloquially refers to prescription-only weight loss injections, including GLP-1 medications like Wegovy and Saxenda, plus the newer dual-action Mounjaro. Costs vary significantly depending on whether you access them through the NHS or privately, and which medication you choose. This guide explains your UK options, how they work, and what you might expect to pay.
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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.
UK-Licensed Weight Loss Injections — Options and Costs
Three weight loss injections are currently licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Each works differently and has different costs.
Mounjaro is a dual GIP and GLP-1 receptor agonist — the newest option. It's a once-weekly injection starting at 2.5 mg, escalating to a maximum of 15 mg. Clinical trials showed average weight loss of 15–21% of body weight, though individual results vary significantly. Private cost typically ranges from £150–£250 per month depending on dose.
Wegovy (semaglutide) is a GLP-1 receptor agonist — a once-weekly injection escalating from 0.25 mg to 2.4 mg maximum. Average weight loss in trials was approximately 15% of body weight alongside lifestyle changes. Private cost typically ranges from £129–£180 per month.
Saxenda (liraglutide) is also a GLP-1 agonist but requires a daily injection, escalating from 0.6 mg to 3 mg. It's the oldest of the three options. Average weight loss is typically 5–10% of body weight. Private cost is usually £100–£150 per month, making it the most affordable option.
All three are prescription-only and require clinical assessment before dispensing. Use our GLP-1 weight loss calculator to explore 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 — Eligibility and Reality
NHS access: All three medications are theoretically available on the NHS through specialist tier 3 weight management services, but real-world access varies dramatically by region. You must be referred by your GP to a specialist weight management service — you cannot request them directly. Waiting lists in many areas are months to years. NHS eligibility typically requires a BMI of 30 or above (or 27+ with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea). South Asian, Chinese, Black African, and Black Caribbean adults may qualify at BMI 27.5 or above due to higher health risks at lower weights.
Private access: Available through UK-licensed online prescribing services. You complete an online health assessment, a registered prescriber reviews it, and if approved, the prescription is dispensed by a GPhC-registered pharmacy. This typically costs £25–£50 for the consultation plus the medication cost. Private access doesn't require a GP referral and is usually much faster — often within days. Check that any provider is MHRA-registered and uses UK-licensed prescribers.
Use our BMI calculator above to check your personal BMI and see which eligibility bracket you fall into.
- 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's the cheapest weight loss injection available in the UK?
Saxenda (liraglutide) is typically the most affordable privately at £100–£150 per month. However, it requires a daily injection rather than once weekly. NHS costs are free but access is limited. On average, weight loss with Saxenda is 5–10% of body weight — lower than Mounjaro or Wegovy.
Can I get fat jabs on the NHS for free?
Yes, theoretically. All three medications are NHS-licensed, but access is limited to specialist tier 3 weight management services through GP referral only. Waiting lists are long in many areas — sometimes over a year. Ask your GP about your local NHS weight management service and eligibility.
How much does Mounjaro cost privately in the UK?
Mounjaro costs typically range from £150–£250 per month depending on dose. The starting dose (2.5 mg) is cheaper than the maximum dose (15 mg). Some providers offer loyalty discounts or multi-month packages. Always confirm the full cost including consultation fees before ordering.
Are fat jab costs covered by private health insurance?
Most private health insurance policies do not cover weight loss medications, even if you have coverage for other treatments. Check your specific policy or contact your insurer directly. Some policies may cover related conditions like type 2 diabetes management, but weight loss itself is usually excluded.
What happens if I stop taking weight loss injections?
Weight typically begins returning once you stop. Clinical trials show that people who discontinued the medication regained most weight within 6–12 months. These medications work alongside sustained lifestyle changes — diet and exercise remain essential. Discuss long-term plans with your prescriber.
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.