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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Fat Loss Pills in the UK — Your Complete Health Guide
Fat loss pills available in the UK are prescription-only medicines that work by helping reduce appetite and support weight management alongside lifestyle changes. The main licensed options are GLP-1 receptor agonists like Wegovy (semaglutide) and Mounjaro (tirzepatide), which are regulated by the MHRA and prescribed following a clinical assessment. Many people search for fat loss pills hoping for a structured approach, but the evidence shows that prescription weight management medications work best when combined with a reduced-calorie diet and increased physical activity. Understanding what's actually available, how these medications work, and whether they're suitable for you requires accurate UK health information rather than marketing claims. This guide covers the facts.
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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.
What Fat Loss Pills Are Actually Available in the UK?
The UK has strict medicines regulation through the MHRA, so only a limited number of weight loss medications are licensed for use. Wegovy (semaglutide) is a once-weekly injection licensed for weight management in adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Mounjaro (tirzepatide) is a newer once-weekly injection that works via a dual mechanism affecting two hormone pathways. Saxenda (liraglutide) is a daily injection also licensed for weight management. All three are prescription-only medicines available through NHS specialist weight management services or private prescribers following a clinical assessment. Important: weight loss tablets like orlistat (Xenical) are available over-the-counter but work differently — they reduce fat absorption in the digestive system rather than affecting appetite signals. Unregulated "fat loss pills" sold online are often ineffective and potentially unsafe. Use our free BMI calculator to check whether you might be eligible for prescription options based on NHS thresholds.
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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 Do Prescription Fat Loss Pills Actually Work?
Prescription weight loss injections available in the UK contain active ingredients that mimic natural hormones regulating appetite and blood sugar. Wegovy contains semaglutide, a GLP-1 receptor agonist that signals to your brain that you're full, slows digestion, and reduces food cravings. Clinical trials (the STEP studies) showed Wegovy helped people lose an average of around 15% of their body weight over 68 weeks — though individual results vary significantly. Mounjaro works via a dual GIP and GLP-1 mechanism and showed approximately 15–21% average weight loss in clinical trials. Neither medication "burns fat" directly; both work by reducing appetite and supporting a calorie deficit. They are always prescribed alongside dietary changes and physical activity, never as a replacement for lifestyle modification. Track your weight loss journey using our free progress tracker as you make changes.
- 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 fat loss pills available without a prescription in the UK?
Some weight loss products are available over-the-counter (like orlistat), but the most effective prescription-only options — Wegovy, Mounjaro, and Saxenda — require a prescription from a GP or licensed prescriber following a clinical assessment. Unregulated pills sold online should be avoided as they're often ineffective and may be unsafe.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes (doses up to 2mg) and using it for weight loss is off-label. Wegovy is specifically licensed for weight management in the UK at higher doses up to 2.4mg. Always use the medication licensed for your intended use.
How much weight will I lose on fat loss pills?
Clinical trials show average weight loss of 15–21% of body weight with prescription medications, but individual results vary significantly. Some people lose more, others less. Weight loss depends on the medication, your dose, adherence, diet, and physical activity. Your prescriber can discuss realistic expectations for you.
Are fat loss pills safe for long-term use?
Licensed prescription weight loss medications have been tested for safety in clinical trials, but like all medicines they have potential side effects — mainly nausea, diarrhoea, and constipation initially. Your GP or prescriber will assess whether they're safe for you personally and monitor you during treatment.
How do I access fat loss pills through the NHS?
NHS access is through specialist tier 3 weight management services, usually via GP referral. Availability varies by region and waiting times can be long. Private prescribers also offer these medications following an online clinical assessment. Use our free BMI calculator to check your eligibility based on NHS thresholds.
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.