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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Prescribed Weight Loss Pills in the UK
Prescribed weight loss pills are prescription-only medications that can support weight management alongside diet and exercise. In the UK, the most commonly prescribed options are GLP-1 receptor agonist injections like Wegovy (semaglutide), which may help reduce appetite and support feeling fuller after meals. Access is through NHS specialist services or private online prescribing following a clinical assessment. Individual results vary, and these medications work best alongside reduced-calorie diet and increased physical activity. Your GP can advise whether prescription weight loss treatment is appropriate for your individual health needs.
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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.
Types of Prescribed Weight Loss Medication
Three main prescription weight loss medications are currently licensed in the UK for weight management:
- Wegovy (semaglutide) — a once-weekly GLP-1 injection with doses from 0.25 mg to 2.4 mg. In clinical trials, it helped participants lose an average of around 15% of their body weight over 68 weeks alongside lifestyle changes.
- Mounjaro (tirzepatide) — a once-weekly dual GIP and GLP-1 receptor agonist injection with doses up to 15 mg. Clinical trial data showed average weight loss of approximately 15–21% of body weight, though results vary significantly between individuals.
- Saxenda (liraglutide) — a daily GLP-1 injection with doses up to 3 mg, though less commonly prescribed than the weekly options.
All three are prescription-only and available only after a clinical assessment confirms you meet eligibility criteria. 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.
UK Eligibility and How to Access Prescription Weight Loss Pills
To be eligible for prescribed weight loss pills in the UK, you typically need 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, prediabetes, high blood pressure, or obstructive sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have access at lower BMI thresholds due to higher health risks at lower weights.
NHS access: Referral through your GP to a specialist tier 3 weight management service. Availability varies significantly by region, and waiting lists can be lengthy. Private access: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, and dispensed by a registered pharmacy. Check your BMI using our free BMI calculator above to understand where you fall on the UK health scale.
- 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 prescribed weight loss pills safe?
Prescription weight loss medications have been clinically tested and approved by the MHRA. Like all medicines, they can have side effects — commonly nausea, diarrhoea, and constipation — which often improve with time. Serious side effects are uncommon but can occur. A prescriber will assess whether a medication is safe for your individual health before issuing a prescription.
Can I get weight loss pills on the NHS?
Yes, but access varies by region. NHS specialist weight management services (tier 3) can prescribe licensed weight loss medications. However, referral pathways and waiting lists differ significantly across England, Scotland, Wales, and Northern Ireland. Your GP can advise on local NHS options and may refer you if you meet eligibility criteria.
How quickly do prescribed weight loss pills work?
Results vary between individuals. Weight loss typically begins within 4–8 weeks but can take longer for some people. Most prescription weight loss medications require regular dose escalation over several weeks, with maximum benefit usually seen after 12–16 weeks of treatment. Sustainable weight loss is generally 0.5–1 kg per week.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic (used for type 2 diabetes, doses up to 2 mg) is not licensed for weight loss in the UK. Wegovy (doses up to 2.4 mg) is the licensed weight management version. Using Ozempic for weight loss would be off-label. Your prescriber will ensure you receive the correct licensed medication for your needs.
Do I need to diet and exercise while taking prescribed weight loss pills?
Yes. These medications work best alongside a reduced-calorie diet and increased physical activity. Clinical trials showed weight loss results were achieved with lifestyle changes combined with medication. Track your progress using our free progress tracker to monitor both weight changes and lifestyle improvements over time.
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.