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
GLP-1 Injection — UK Health Information
GLP-1 injections are prescription-only weight management medications licensed in the UK to help adults lose weight. They work by mimicking a natural hormone your gut produces, helping reduce appetite and support feeling fuller. If you're interested in understanding how GLP-1 injections fit into UK weight management options, this guide covers NHS guidance, eligibility, how they work, available medications, and what to expect. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes.
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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.
How GLP-1 Injections Work and UK Availability
GLP-1 (glucagon-like peptide-1) is a natural hormone your body produces after eating. GLP-1 injections mimic this hormone, signalling to your brain that you're satisfied, reducing food cravings, and slowing how quickly food leaves your stomach. This helps many people eat less and feel fuller on smaller portions.
In the UK, three GLP-1 medications are licensed for weight management:
- Wegovy (semaglutide) — 0.25mg to 2.4mg, injected once weekly
- Saxenda (liraglutide) — 0.6mg to 3mg, injected once daily
- Mounjaro (tirzepatide) — technically a dual GIP/GLP-1 agonist, 2.5mg to 15mg weekly
All are prescription-only medicines requiring clinical assessment. Clinical trials showed participants lost an average of 14–21% of body weight alongside reduced-calorie diet and increased physical activity — though individual results vary significantly.
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.
UK Eligibility and NHS Access
You may be eligible for GLP-1 injections in the UK if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at slightly lower BMI thresholds due to higher cardiovascular risk.
Access is available through NHS specialist weight management services (typically tier 3) following GP referral, though availability and waiting times vary by region. Private prescriptions are also available from GPhC-registered online prescribers without NHS referral. Your GP can advise on the best route for your circumstances and help you decide if GLP-1 treatment suits your health needs.
- 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.
Are GLP-1 injections available on the NHS?
GLP-1 injections are approved for NHS prescription through specialist weight management services, but availability varies by region and waiting times can be lengthy. You'll need referral from your GP to a tier 3 specialist service. Private prescription is also available from UK-licensed prescribers without NHS referral.
How much weight can you lose with GLP-1 injections?
Clinical trials showed average weight loss of 14–21% of body weight at the highest doses, alongside lifestyle changes. Individual results vary significantly depending on dose, adherence, diet, and exercise. Use our free weight loss calculator to explore potential outcomes based on your starting weight.
What are the main side effects of GLP-1 injections?
Most common side effects are nausea, diarrhoea, vomiting, and constipation — usually mild and temporary. Serious side effects are rare but include severe stomach pain (possible pancreatitis), gallbladder problems, and serious allergic reactions. Always report any concerning symptoms to your GP or prescriber.
How do I check if I'm eligible for GLP-1 treatment in the UK?
Calculate your BMI using our free BMI calculator on this page. If your BMI is 30 or above, or 27–29.9 with weight-related health conditions, you may be eligible. Speak to your GP about referral to specialist services, or consult a private prescriber for eligibility assessment.
How often do you inject GLP-1 medication?
Wegovy and Mounjaro are once-weekly injections. Saxenda is once daily. All are administered by you at home using a pre-filled injection pen. Your prescriber will train you on correct injection technique before starting treatment.
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.