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
Colon Cleanse for Weight Loss — What Actually Works in the UK
If you're searching for a colon cleanse for weight loss, it's worth knowing that cleanses don't produce meaningful, lasting results. Instead, the NHS and UK healthcare professionals recommend evidence-based approaches to weight management. For eligible adults, prescription weight loss medication combined with lifestyle changes offers clinically proven support. This guide explains what actually works for sustainable weight management in the UK and how to explore prescription options with your GP.
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 Management Options
If you're interested in weight management uk options, three prescription medications are currently licensed in the UK for weight loss in eligible adults:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 hormone pathways. Clinical trials showed participants lost an average of 15–21% of body weight over 72 weeks alongside a reduced-calorie diet.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Evidence demonstrates approximately 15% average body weight loss in clinical trials at the maximum dose.
- Saxenda (liraglutide) — a once-daily GLP-1 injection, an established option for glp-1 weight loss in the UK since 2015.
These are all prescription-only medicines. Each requires a clinical assessment to confirm eligibility. Unlike colon cleanses, these medications work by regulating appetite hormones and are used alongside dietary changes and increased physical activity.
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 Eligibility and How to Get Started
For nhs weight loss medication in the UK, you generally need a BMI of 30 or above, or 27 or above if you have weight-related health conditions such as type 2 diabetes or high blood pressure. Access through the NHS typically involves referral to a specialist tier 3 weight management service via your GP—though waiting times vary significantly by region.
Alternatively, prescription weight loss medication is available privately through UK-licensed prescribers following an online clinical assessment. Start by having a conversation with your GP about whether prescription weight loss medication might be suitable for you. Use our free BMI calculator above to understand your current BMI status. Your GP can discuss which approach—NHS or private—is right for your circumstances.
- 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 colon cleanses lead to lasting weight loss?
Colon cleanses remove water and temporary stool mass, creating short-term weight reduction that returns once you eat normally. They don't address the underlying factors that drive weight gain—appetite regulation, calorie intake, and metabolic health. Any weight lost is water, not fat loss.
What's the difference between a colon cleanse and prescription weight loss medication?
Colon cleanses are unregulated products with no lasting benefit. Prescription medications like Mounjaro and Wegovy work by regulating hunger hormones and are supported by clinical trials showing sustained fat loss. They're prescription-only and require medical assessment—not sold over the counter.
How do I know if I'm eligible for prescription weight management in the UK?
Eligibility generally requires a BMI of 30 or above, or 27 or above with weight-related conditions. Your GP can assess your eligibility based on your health history. Use our free BMI calculator to check your starting point, then discuss options with your GP.
What's the difference between NHS and private prescription weight loss medication?
NHS access is through specialist services (tier 3) via GP referral—waiting times vary by region. Private prescribing is faster but involves costs (typically £129–£320 monthly depending on dose and provider). Both require clinical assessment; both are prescription-only.
Can I use the weight loss calculator on MyWeightCheck to estimate results with GLP-1 medication?
Yes. Our free GLP-1 weight loss calculator helps you estimate potential weight loss at different doses based on clinical trial data. Enter your current weight and the calculator shows projected outcomes—though individual results vary. It's useful for discussing realistic expectations with your GP.
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.