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
Free tracker included with every download this week
How Much Are Fat Jabs in the UK?
Fat jabs—the colloquial UK term for prescription weight loss injections—vary in cost depending on which medication you're prescribed and where you access them. If you're eligible through the NHS, they're free once prescribed by a specialist weight management service, though waiting lists can be lengthy. Privately, they typically cost between £129 and £320 per month depending on the dose and provider. Understanding your options and eligibility is the first step.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Who Is Eligible for Weight Loss Injections in the UK?
Before discussing cost, it's important to know if you're eligible. NHS eligibility generally requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds often apply (from 27.5 or above). Private eligibility is assessed individually by a licensed UK prescriber during an online consultation—criteria are similar but access is faster.
- BMI 30+ without comorbidities (both NHS and private)
- BMI 27–29.9 with weight-related health conditions
- Adults 18+ years old
- Not pregnant, planning pregnancy, or breastfeeding
- Ethnicity-adjusted thresholds apply (lower for certain groups)
Use our free BMI calculator above to check your current BMI and see where you fall on the NHS guidelines. Your BMI is a starting point—a GP or licensed prescriber will assess your full health picture before making recommendations.
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 Routes: Cost, Access & Timeline
NHS route: Weight loss injections are free once prescribed through tier 3 specialist weight management services, but access requires a GP referral and can involve waiting lists of months or even years depending on your region. Availability varies significantly across England, Wales, Scotland, and Northern Ireland.
Private route: Available without NHS referral through online consultations with UK-licensed prescribers, typically costing £129–£320 per month depending on the GLP-1 weight loss medication dose. Private access is faster—often within days—but you pay the full cost. Both routes require a prescription and clinical assessment; neither provides medication without proper evaluation of your health history.
- 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 do fat jabs cost privately in the UK?
Private weight loss injections typically cost between £129 and £320 per month depending on the medication (tirzepatide, semaglutide, or liraglutide) and the dose prescribed. Starting doses are cheaper; maximum doses cost more. Prices vary between providers, so it's worth comparing online prescribing services.
Are fat jabs free on the NHS?
Yes, prescription weight loss injections are free on the NHS once prescribed by a specialist weight management service. However, access requires a GP referral to tier 3 services, and waiting lists can be very long—sometimes many months or longer depending on your region.
What happens during a private consultation for fat jabs?
A UK-licensed prescriber will review your medical history, current medications, height, weight, and BMI. They'll assess whether you're eligible based on NHS-style criteria and check for any contraindications. If approved, a prescription is issued and dispensed by a GPhC-registered pharmacy.
How long does it take to get fat jabs privately vs NHS?
Privately, you can usually receive a prescription within 24–48 hours of consultation and start treatment within days. NHS access depends on your region's tier 3 service capacity; waiting lists often exceed 6–12 months. Both routes require a prescription and clinical assessment.
Can I use my NHS prescription weight loss medication on a private tracker?
Yes, our free progress tracker works with any prescription weight loss medication. Track your weight loss journey from both NHS and private prescriptions in the same place using the tracker on this page.
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.