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
Weight Loss Beyond Detox — What Actually Works in the UK
"Detox" and "cleanse" products are heavily marketed for weight loss, but evidence shows they rarely deliver lasting results. If you're looking for effective weight management in the UK, prescription options are available for eligible adults. This guide explains why detox approaches often fall short, and introduces clinically-proven alternatives including GLP-1 weight loss medications available through the NHS and private prescribing. Understanding your options — and your BMI — is the first step towards sustainable weight management.
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 Prescription Weight Loss Medications
Three GLP-1 and GIP/GLP-1 medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist, once-weekly injection. Clinical trials showed average weight loss of 15–21% of body weight at the highest dose alongside diet and exercise.
- Wegovy (semaglutide) — GLP-1 receptor agonist, once-weekly injection. Average weight loss approximately 15% of body weight in clinical trials.
- Saxenda (liraglutide) — GLP-1 receptor agonist, daily injection. Established medication with long clinical history.
All three are prescription-only medicines. You're eligible if you have a BMI of 30 or above, or BMI of 27–29.9 with a weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. Individual results vary — prescription weight loss medication works best alongside reduced-calorie diet and increased physical activity. Calculate your BMI using our free BMI calculator above to check your starting point.
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: How to Access Weight Loss Support
NHS route: Referral to a specialist tier 3 weight management service. Speak to your GP about availability in your area — access varies significantly by region and waiting lists can be lengthy.
Private route: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, dispensed by a GPhC-registered pharmacy. No NHS referral needed. Available without waiting lists.
Whether you pursue NHS or private options, a qualified healthcare professional will assess whether prescription weight loss medication is suitable for you. They'll discuss your health history, current medications, and weight loss goals. Track your weight loss progress using our free progress tracker to monitor your results over time. Whatever approach you choose, sustainable nhs weight loss requires lifestyle changes alongside any medication.
- 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.
Why don't detox cleanses work for lasting weight loss?
Detox products claim to "remove toxins", but your liver and kidneys naturally eliminate waste. Any initial weight loss from cleanses is usually water loss, not fat loss, and returns quickly. Evidence-based weight management requires sustained calorie deficit and lifestyle changes, not temporary detoxes. For lasting results, prescription options and lifestyle support are more effective.
Am I eligible for prescription weight loss medication in the UK?
Yes, if your BMI is 30 or above, or 27–29.9 with a weight-related health condition like type 2 diabetes or high blood pressure. For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds apply. Your GP can assess your eligibility, or a private prescriber can evaluate you online. Use our BMI calculator to check your starting point.
How much weight can I expect to lose with GLP-1 medication?
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 works best alongside a reduced-calorie diet and increased physical activity. Your prescriber will discuss realistic expectations for your situation.
Can I get GLP-1 medication through the NHS?
Yes, Mounjaro and Wegovy are now approved for NHS prescription through specialist tier 3 weight management services. Access varies by region — some areas have limited availability and long waiting lists. Ask your GP about referral to your local specialist weight management service to check eligibility and waiting times.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Both are once-weekly injections. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but results vary individually. Your prescriber will recommend the most suitable option for you.
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.