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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Weight Loss Jabs On NHS: What You Need To Know
Weight loss jabs—prescription injections for weight management—are available in the UK through both NHS specialist services and private providers. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions, you may be eligible for these medications. The NHS offers access through tier 3 specialist weight management services, though availability varies by region. This guide explains the licensed options, eligibility criteria, and how to find out if prescription weight loss 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.
UK-Licensed Weight Loss Injections Available
Three prescription weight loss injections are licensed in the UK:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 agonist, once-weekly injection, doses from 2.5 mg to 15 mg. Clinical trials showed average weight loss of 15–21% of body weight at maximum dose.
- Wegovy (semaglutide) — GLP-1 agonist, once-weekly injection, doses from 0.25 mg to 2.4 mg. Evidence suggests average weight loss of approximately 15% of body weight.
- Saxenda (liraglutide) — GLP-1 agonist, once-daily injection, doses from 0.6 mg to 3 mg. Typically produces modest weight loss compared to newer options.
All three are prescription-only medicines requiring a clinical assessment before use. Individual results vary significantly based on diet, physical activity, and personal metabolism. Try our GLP-1 weight loss calculator to estimate potential weight loss 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 Access vs Private: How To Get Started
NHS route: Ask your GP for a referral to your local tier 3 specialist weight management service. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Waiting times vary significantly by region—some areas have delays of several months. NHS prescriptions are free once approved.
Private route: Online consultations with UK-licensed prescribers are available, with prescriptions dispensed by GPhC-registered pharmacies. No NHS referral needed. Costs range from approximately £129–£320 monthly depending on dose.
Next step: Check your BMI using our free BMI calculator above, then speak with your GP about your weight management options and eligibility.
- 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.
Am I eligible for weight loss jabs on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27 or above with at least one weight-related health condition (type 2 diabetes, high blood pressure, heart disease, or sleep apnoea). Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Ask your GP for a referral to your local specialist weight management service to check your eligibility.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 medication, while Wegovy (semaglutide) is a GLP-1 only medication. Clinical trials suggest Mounjaro may produce slightly greater average weight loss (15–21% vs 15%), but individual results vary. Both are once-weekly injections. Your prescriber will assess which is more suitable for your circumstances.
How long does it take to see results with weight loss jabs?
Weight loss typically begins within 2–4 weeks and continues over several months as your dose is increased. Most significant results appear between weeks 8 and 20. The pace of loss varies between individuals based on diet, exercise, metabolism, and other factors. Sustainable weight loss alongside these medications occurs at approximately 0.5–1 kg per week.
Are weight loss injections safe?
All three UK-licensed medications have undergone rigorous clinical trials and safety assessments. Common side effects include nausea, diarrhoea, and constipation—typically mild and temporary. Serious side effects are rare but can include pancreatitis. A prescriber will assess your individual health history and decide if the medication is safe and appropriate for you.
What happens when I stop taking weight loss jabs?
Weight regain is common after stopping these medications if diet and exercise habits don't change permanently. These are tools to support behaviour change, not permanent solutions. Most people who maintain the lifestyle changes (reduced calorie intake, regular activity) keep most of their weight loss. Your GP or prescriber can advise on a long-term plan.
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.