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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Different Weight Loss Injections Available in the UK
If you're exploring weight management UK options, prescription weight loss injections may be available to you. Three medications are currently licensed in the UK for weight management in adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are prescription-only medicines that work by mimicking natural hormones to help reduce appetite and support sustainable weight loss alongside lifestyle changes. This guide explains how each injection works, who is eligible, and how to access them through the NHS or privately.
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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 Explained
Mounjaro (tirzepatide) is a once-weekly injection that activates two hormone pathways — GIP and GLP-1. In clinical trials, participants lost an average of 15–21% of their body weight, though individual results vary significantly. The maximum dose is 15 mg weekly.
Wegovy (semaglutide) is also a once-weekly GLP-1 injection, with a maximum dose of 2.4 mg. Clinical trial data showed average weight loss of around 15% body weight alongside a reduced-calorie diet and increased physical activity. Results vary between individuals.
Saxenda (liraglutide) is a daily GLP-1 injection (not weekly) with a maximum dose of 3 mg. It has a longer history of use and may be offered in some NHS weight management services, though Mounjaro and Wegovy are now the primary prescription options.
All three work by helping you feel fuller after smaller meals, reducing food cravings, and supporting a sustained calorie deficit for weight loss.
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 and Private Access — How to Get Weight Loss Injections
For NHS prescription weight loss medication, you need referral to a specialist tier 3 or tier 4 weight management service through your GP. NHS availability varies significantly by region, and waiting lists can be long in many areas. Eligibility typically 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 sleep apnoea.
For private access, you can have an online consultation with a UK-licensed prescriber without NHS referral. If clinically appropriate, a prescription is issued and dispensed by a GPhC-registered pharmacy. Private costs typically range from £129–£320 per month depending on dose.
Whichever route you choose, a prescriber will assess your individual health and suitability before prescribing. Our GLP-1 weight loss calculator can help you estimate potential weight loss at different doses.
- 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 is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways — GIP and GLP-1 — while Wegovy (semaglutide) activates GLP-1 only. Mounjaro typically produces slightly higher average weight loss (15–21% vs 15%), but individual results vary. Both are once-weekly injections licensed for UK weight management.
Am I eligible for prescription weight loss injections?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). Lower BMI thresholds (27.5+) may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP or prescriber can assess your individual eligibility.
How quickly will I lose weight on these injections?
The NHS recommends weight loss of 0.5–1 kg per week as sustainable. Clinical trials show average weight loss of 15–21% over several months, but individual results vary significantly. Weight loss injections work alongside a reduced-calorie diet and increased physical activity — they are not a standalone treatment.
Are weight loss injections available on the NHS?
Yes, Mounjaro and Wegovy are approved for NHS use through specialist weight management services. However, availability varies by region and waiting lists can be lengthy. Private prescription options are also available through online consultations with UK-licensed prescribers.
What happens if I stop taking a weight loss injection?
If you stop the injection, appetite-suppressing effects typically wear off within days to weeks, and weight regain is common if lifestyle changes are not maintained. Long-term weight management requires ongoing dietary and activity habits. Your prescriber can discuss the best approach for your situation.
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.