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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What Weight Loss Pills Actually Work in the UK?
If you're searching for weight loss pills that actually work, the evidence points to prescription medications rather than over-the-counter supplements. In the UK, three prescription-only medicines are licensed for weight management: Mounjaro, Wegovy, and Saxenda. These are supported by clinical trial data showing meaningful weight loss results. However, they're not suitable for everyone, and access depends on eligibility criteria and whether you go through the NHS or private prescribing. This guide explains which options are available, how they work, and how to find out if you qualify.
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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.
Prescription Weight Loss Medications Licensed in the UK
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist—a once-weekly injection that activates two natural hormone pathways to help regulate appetite and reduce food cravings. Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks, with results varying by dose and individual response. Wegovy (semaglutide) is a GLP-1 receptor agonist—also a once-weekly injection—with clinical trial data showing approximately 14.9% average weight loss at the maximum dose. Saxenda (liraglutide) is an older GLP-1 injection given daily rather than weekly, with more modest average weight loss around 5–10%.
- All three are prescription-only and require clinical assessment before being prescribed
- All must be used alongside a reduced-calorie diet and increased physical activity—they are not standalone solutions
- Individual results vary significantly; clinical trial averages do not assures specific outcomes
- Common side effects include nausea, diarrhoea, and constipation, typically mild and temporary
Forget unproven supplements or fad pills—the evidence supports these licensed prescription options for weight management uk adults meeting eligibility criteria.
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 vs Private Access and Eligibility
In the UK, you can access prescription weight loss medication through the NHS or private prescribing. NHS access: You must be referred to a specialist tier 3 weight management service by your GP. 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. Waiting lists for NHS specialist services can be lengthy in many areas. Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, without needing an NHS referral.
Calculate your BMI using our free BMI calculator to see where you stand, then discuss your results with your GP or a licensed prescriber to explore whether prescription medication is appropriate 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.
Do weight loss pills really work?
Yes, prescription weight loss medications licensed in the UK have strong clinical evidence. Mounjaro and Wegovy show average weight loss of 15–21% and 15% respectively in clinical trials—significantly more than unproven supplements. However, individual results vary, and they work best alongside diet and exercise changes, not as standalone solutions.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro is a dual GIP+GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Clinical trial data suggests slightly higher average weight loss with Mounjaro, though direct comparisons are limited. Your prescriber will assess which suits you best.
Can I get weight loss pills on the NHS?
Yes, prescription weight management medicines are available through NHS specialist services. You'll need a GP referral to a tier 3 weight management service and must meet eligibility criteria (typically BMI 30+, or 27–29.9 with health conditions). NHS availability varies by region and waiting lists can be long.
How much do weight loss injections cost privately in the UK?
Private prescription weight loss injections typically cost £129–£320+ per month depending on the medication and dose. Prices vary between providers. Compare quotes from GPhC-registered pharmacies offering online prescribing, and always ensure a licensed prescriber has assessed you first.
What are the side effects of weight loss pills in the UK?
Common side effects of prescription weight loss medications include nausea, diarrhoea, vomiting, and constipation—usually mild and temporary. Serious side effects are rare but can include severe stomach pain (pancreatitis risk) or gallbladder problems. Always discuss side effects with your prescriber and report any concerns.
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.