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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Weight Loss Pills in the UK — What You Need to Know
Weight loss pills are prescription-only medications available in the UK to support weight management for eligible adults. The most commonly prescribed options are GLP-1 receptor agonist injections like Wegovy (semaglutide) and Mounjaro (tirzepatide), which work by helping reduce appetite and support feeling fuller after eating. Unlike over-the-counter supplements, prescription weight loss medications require a clinical assessment from a GP or licensed prescriber, and they're typically used alongside reduced-calorie diets and increased physical activity. This UK health guide explains how they work, eligibility criteria, and how to access them through NHS or private routes.
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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 Prescription Weight Loss Medications Work
The main weight loss pills prescribed in the UK are GLP-1 receptor agonist medications. Wegovy (semaglutide) activates the GLP-1 hormone pathway, which helps reduce appetite, decrease food cravings, and support feeling fuller after smaller meals. In clinical trials (the STEP-1 trial), patients using Wegovy at the maximum 2.4mg dose lost an average of approximately 15% of their body weight over 68 weeks, though individual results vary significantly.
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways, which may provide additional appetite-suppressing benefits. Clinical trial data showed average weight loss of around 15–21% depending on the dose used.
- Both are once-weekly injections, not oral tablets
- Both require prescription and clinical assessment
- Both work best alongside a reduced-calorie diet and increased physical activity
- Individual results vary — weight loss is not assured
These medications slow how quickly food leaves the stomach and support fat utilisation, helping to create and maintain a calorie deficit.
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.
Who Can Access Weight Loss Pills in the UK?
Eligibility for prescription weight loss medication in the UK depends on BMI and health status. Adults with a BMI of 30 or above (obesity), or a BMI of 27–29.9 with at least one weight-related health condition, may be eligible. Weight-related conditions include type 2 diabetes, high blood pressure, abnormal blood fats, sleep apnoea, or history of cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidance recommends lower thresholds — eligibility may start at BMI 27.5 or above, because these groups face higher health risks at lower BMI levels.
Use our free BMI calculator above to check your personal BMI instantly. You cannot access prescription weight loss pills without a clinical assessment from a GP or licensed prescriber, who will evaluate your individual health circumstances.
Access to weight loss pills in the UK works through two main routes. NHS route: Referral to a tier 3 specialist weight management service from your GP. Availability varies significantly by region, and waiting lists can be lengthy. Private route: Online consultation with a UK-licensed prescriber, prescription issued if clinically suitable, then dispensed by a GPhC-registered pharmacy. Private prescriptions typically cost £129–£320 per month depending on medication and dose. Neither route assures prescription — clinical assessment is always required. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses.
- 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 in the UK?
Yes, but access is limited. Prescription weight loss medications are available through NHS specialist weight management services (tier 3), but only following referral from your GP and clinical assessment. Availability and waiting times vary significantly by region. Private prescribing offers faster access without NHS referral.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Wegovy is licensed for weight management (up to 2.4mg dose), while Ozempic is licensed for type 2 diabetes (up to 2mg dose). Using Ozempic for weight loss is off-label. Always ensure your prescription clearly states Wegovy if weight loss is your goal.
How much weight can I expect to lose with weight loss pills?
Clinical trials show average weight loss of around 15–21% of body weight over 68 weeks, though individual results vary significantly. Some people lose more, some less. Weight loss depends on your starting weight, adherence to medication, diet, and physical activity. Results are not assured.
Do weight loss pills work without diet and exercise?
No. Weight loss medications are most effective alongside a reduced-calorie diet and increased physical activity. They support appetite reduction and help create a calorie deficit, but lifestyle changes are essential for sustainable results.
Can I buy weight loss pills online without a prescription?
No. Prescription weight loss medications like Wegovy and Mounjaro are prescription-only in the UK. You cannot legally obtain them without a prescription from a UK-licensed prescriber following a clinical assessment. Always use GPhC-registered pharmacies.
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.