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 Injections in the UK: Reviews and Your Options
Weight loss injections are prescription-only medications that can help adults manage excess weight when used alongside diet and exercise. In the UK, three GLP-1 and GIP receptor agonist medications are licensed for weight management: Mounjaro, Wegovy, and Saxenda. Each has different evidence, dosing schedules, and availability through both NHS specialist services and private prescribing. Understanding your options and eligibility is the first step toward discussing weight management with your GP.
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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 and Their Evidence
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — the newest option in the UK. Clinical trials (SURMOUNT-1) showed participants lost an average of 15–21% of their body weight over 72 weeks at the highest dose, alongside a reduced-calorie diet and increased physical activity. It's administered as a once-weekly injection, starting at 2.5 mg and escalating to a maximum of 15 mg.
Wegovy (semaglutide) is a GLP-1 receptor agonist manufactured by Novo Nordisk. The STEP-1 trial demonstrated average weight loss of approximately 15% of body weight at the highest dose (2.4 mg). Like Mounjaro, it's a once-weekly injection but requires a slower dose escalation over 16 weeks.
Saxenda (liraglutide) is also a GLP-1 medication but administered as a daily injection rather than weekly. Clinical evidence shows comparable weight loss results, though daily dosing may be less convenient for some users.
Important: Individual results vary significantly. These are average outcomes from clinical trials conducted alongside lifestyle changes — weight loss is not assured.
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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: How to Get Weight Loss Injections in the UK
NHS access: Weight loss medications are available through specialist tier 3 and tier 4 weight management services, typically accessed via GP referral. NICE has approved tirzepatide (Mounjaro) for NHS use, but availability varies by region and integrated care board (ICB). Waiting times for NHS specialist services can be several months to over a year in many areas.
Private access: You can obtain a prescription through a GPhC-registered online pharmacy following a clinical assessment with a UK-licensed prescriber — no NHS referral required. Costs range from approximately £129–£320 per month depending on the dose and provider.
To find out if you're eligible, speak with your GP. Use our free BMI calculator above to check your starting point. Eligibility depends on BMI (30 or above, or 27–29.9 with weight-related health conditions) and individual health assessment.
- 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 weight loss injections safe?
Yes, when prescribed appropriately following clinical assessment. All three UK-licensed medications have undergone rigorous safety testing. Common side effects include nausea and digestive changes, usually mild and temporary. Serious side effects are rare. Your prescriber will assess whether a weight loss injection is suitable for your individual health profile.
How much weight can you lose with weight loss injections?
Clinical trials show average weight loss of 15–21% of body weight over 12–18 months, depending on the medication and dose. However, individual results vary significantly. Weight loss depends on the medication, your starting weight, adherence, diet, and physical activity. Some people lose more, others less.
Can I get weight loss injections on the NHS?
Yes, if you meet eligibility criteria and are referred to a specialist weight management service. Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Availability and waiting times vary significantly by region. Ask your GP about local NHS services and waiting lists.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with slightly higher average weight loss in trials (15–21% vs Wegovy's ~15%). Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections. Mounjaro starts at 2.5 mg; Wegovy at 0.25 mg. Both require clinical assessment and prescription.
How do I know if weight loss injections are right for me?
Your GP or a licensed prescriber can assess your eligibility based on your BMI, health history, and any weight-related conditions. Calculate your BMI using our free tool above, then speak with your GP about whether prescription weight management might help. They'll discuss benefits, risks, and whether lifestyle support or medication is most appropriate for you.
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.