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
Are Weight Loss Pills Safe? UK Prescription Options Explained
Weight loss pills can be safe when prescribed and monitored by a healthcare professional, but not all options available online are appropriate or regulated. In the UK, prescription weight management medications including Mounjaro and Wegovy are licensed and clinically tested. These require a clinical assessment before prescription and work alongside diet and exercise. If you're considering weight loss medication, understanding your eligibility and the NHS options available is essential. This guide covers safe, regulated weight loss pills in the UK context.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 — What's Safe and Effective
The UK's medicines regulator (MHRA) has approved three prescription-only medications specifically for weight management. Mounjaro (tirzepatide) is a once-weekly injection with dual GIP and GLP-1 action — clinical trials showed participants lost an average of 15–21% of body weight alongside reduced-calorie diet and increased physical activity. Wegovy (semaglutide) is a once-weekly GLP-1 injection — average weight loss in trials was approximately 15% of body weight. Saxenda (liraglutide) is a daily GLP-1 injection with similar evidence. All three require a prescription from a UK-licensed prescriber and a clinical assessment to confirm you're suitable. Individual results vary significantly. These medications are evidence-based and monitored by the MHRA, making them fundamentally different from unregulated supplements or unlicensed pills sold online.
- Must have a BMI of 30 or above, or 27–29.9 with weight-related health conditions
- Require ongoing clinical monitoring
- Work best alongside lifestyle changes
- Available through NHS specialist services or private prescribing
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 — Finding Out If You're Eligible
Access to prescription weight loss medication in the UK differs significantly between NHS and private routes. Through the NHS, you can be referred to your local tier 3 specialist weight management service by your GP — though waiting lists vary by region and can be lengthy. Privately, you can have an online consultation with a UK-licensed prescriber without an NHS referral; if clinically appropriate, a prescription is issued and dispensed by a GPhC-registered pharmacy. Your GP can assess your personal eligibility based on your BMI, health history, and weight-related conditions. The key safety question isn't whether weight loss pills exist, but whether they're prescribed appropriately for your individual situation. Our free BMI calculator can help you check where you sit against NHS eligibility thresholds — use this as a starting point for a conversation with your GP or a licensed prescriber.
- 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 available on the NHS?
Yes. Prescription weight loss medications including Mounjaro and Wegovy are approved by NICE for use within NHS specialist weight management services. Access varies by region and typically requires referral from your GP to a tier 3 or tier 4 service. Waiting lists can be lengthy in some areas.
What makes prescription weight loss medication safer than online pills?
UK-licensed medications like Mounjaro and Wegovy are approved by the MHRA, clinically tested, and require prescription from a qualified healthcare professional. You receive a clinical assessment before use. Unregulated pills sold online lack this oversight and may contain harmful substances.
How effective are weight loss injections compared to pills?
Mounjaro and Wegovy are injectable medications (not pills) with strong clinical evidence — average weight loss of 15–21% of body weight in trials. Effectiveness depends on your individual health, adherence, and lifestyle changes. Results vary significantly between people.
Can I get weight loss medication privately without waiting for NHS?
Yes. Private prescribers can assess you online without NHS referral. If eligible, they issue a prescription dispensed by a GPhC-registered pharmacy. Costs typically range from £129–£320 monthly depending on medication and dose.
What's the safest way to start weight loss medication?
Always begin with a clinical assessment from a licensed prescriber (GP or private) — never purchase unregulated pills online. They'll review your health history, check eligibility, explain side effects, and monitor your progress. Medication works best alongside diet, exercise, and behaviour change.
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.