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
Best Weight Loss Treatment in the UK
If you're looking for the best weight loss treatment, prescription medication may be an option if you meet NHS eligibility criteria. The UK has several licensed weight management medications available through both NHS specialist services and private prescribing. Understanding what's available, how they work, and whether you're eligible is the first step towards sustainable weight management. This guide covers the prescription options, eligibility requirements, and how to explore what might work 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 Medications
Three prescription-only medications are currently licensed in the UK for weight management. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist — in clinical trials, participants lost an average of 15–21% of their body weight. Wegovy (semaglutide) is also a once-weekly GLP-1 injection, with trial data showing average weight loss of around 15% alongside a reduced-calorie diet and increased physical activity. Saxenda (liraglutide) is a daily GLP-1 injection option.
All three require a prescription from a licensed prescriber and a clinical assessment to confirm suitability. Individual results vary significantly — these are averages from clinical trials. Weight loss medication works best alongside lifestyle changes, not as a replacement for them. Use our free GLP-1 weight loss calculator to explore potential outcomes 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 Eligibility and Access
On the NHS, prescription weight loss medication may be available if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, hypertension, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply.
Access is through specialist tier 3 weight management services — typically requiring a GP referral. Waiting times vary significantly by region. If you'd like to explore your eligibility, start a conversation with your GP about weight management support. Alternatively, private prescribing offers faster access without waiting lists, though costs apply. Either way, a clinical assessment determines whether treatment is right for you.
- 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's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections for weight management. Mounjaro uses dual GIP and GLP-1 action (average weight loss 15–21%), whilst Wegovy uses GLP-1 only (average weight loss ~15%). Clinical trial results differ slightly, but individual outcomes vary considerably. Your prescriber will help determine which is more appropriate for you.
How long does weight loss medication take to work?
Most people begin noticing effects within 2–4 weeks, though significant weight loss typically takes 8–12 weeks. Doses are usually increased gradually every 4 weeks. Full benefits are usually seen after 6–12 months of treatment at the maintenance dose.
Can I get weight loss injections on the NHS?
Yes, if you meet eligibility criteria (BMI ≥30, or ≥27.5 with weight-related conditions). Access is through specialist NHS weight management services via GP referral. Availability and waiting times vary by region. Private prescribing offers an alternative if you prefer faster access.
What happens if I stop taking weight loss medication?
Weight typically begins to return when you stop treatment. Weight loss medications work best as part of long-term weight management, combined with sustained dietary and activity changes. Your prescriber can discuss how long treatment might continue.
Are weight loss injections safe?
All three licensed UK medications have undergone rigorous clinical trials and safety monitoring. Common side effects include nausea and digestive changes, usually mild and temporary. Serious side effects are rare. Always discuss individual health factors with your prescriber — certain conditions may mean medication isn't suitable.
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.