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
What Are the Best Weight Loss Pills Available in the UK?
When it comes to prescription weight loss medication in the UK, the best option depends on your individual health, BMI, and medical history. The most effective prescription weight loss pills currently licensed in the UK are GLP-1 receptor agonists like Wegovy (semaglutide) and Mounjaro (tirzepatide), both of which work by helping regulate appetite and support weight management alongside dietary changes. These are prescription-only medicines that require a clinical assessment before use. Our free BMI calculator can help you check whether you might be eligible for prescription weight loss treatment based on current NHS guidelines.
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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 Do the Best Prescription Weight Loss Pills Work?
GLP-1 receptor agonist medications are currently the most effective prescription weight loss pills available for UK weight management. They work by mimicking the natural hormone GLP-1, which regulates appetite and blood sugar control.
- Wegovy (semaglutide) — GLP-1 agonist, once-weekly injection, approved for adults with BMI ≥30 or BMI ≥27 with weight-related health conditions. Clinical trials showed average weight loss of approximately 15% body weight over 68 weeks.
- Mounjaro (tirzepatide) — Dual GIP + GLP-1 agonist, once-weekly injection. Clinical trials demonstrated average weight loss of 15–21% body weight depending on dose.
- Saxenda (liraglutide) — GLP-1 agonist, daily injection, maximum dose 3mg per day.
All three are prescription-only medicines requiring a clinical assessment. They work most effectively alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly.
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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.
How to Access the Best Weight Loss Pills in the UK
Access to prescription weight loss pills in the UK depends on your BMI and health profile. According to NHS weight loss guidance, you may be eligible if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may have access at lower BMI thresholds due to higher health risks at these weights.
Two main routes exist: NHS specialist services (via GP referral to tier 3 weight management services) or private prescribing through GPhC-registered online pharmacies following a clinical assessment. Try our GLP-1 weight loss calculator to estimate potential outcomes at different doses, and use our free progress tracker to monitor your weight loss journey once treatment begins.
- 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 pills safe?
Prescription weight loss pills like Wegovy and Mounjaro are licensed medications that have undergone clinical trials demonstrating safety and efficacy. However, they are not suitable for everyone. Side effects (nausea, diarrhoea, constipation) are common initially but often improve over time. Always discuss safety with your prescriber, especially if you have existing health conditions or take other medications.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 agonist, while Mounjaro (tirzepatide) is a dual GIP + GLP-1 agonist. Both are once-weekly injections, but Mounjaro has shown slightly higher average weight loss (15–21%) compared to Wegovy (approximately 15%) in clinical trials. Choice depends on individual assessment, medical history, and prescriber recommendation.
Can I get weight loss pills on the NHS?
Yes, prescription weight loss medications are available through NHS specialist tier 3 weight management services, but availability varies by region and there may be waiting lists. You must be referred by your GP. Private prescribing is available more quickly through online services but involves out-of-pocket costs. Check with your local ICB for NHS availability in your area.
How much weight will I lose on weight loss pills?
Clinical trials show average weight loss of 15–21% of body weight depending on the medication and dose. However, individual results vary significantly. Weight loss requires the medication to be used alongside a reduced-calorie diet and increased physical activity. Use our GLP-1 weight loss calculator to get a personalised estimate based on your current weight and chosen dose.
Are there non-injectable weight loss pills available in the UK?
Currently, the most effective prescription weight loss medications licensed in the UK are injectable (Wegovy, Mounjaro, Saxenda). Older oral medications like orlistat are available over-the-counter but have lower efficacy. Always speak to your GP or prescriber about which option is best for your situation and health profile.
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.