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
Should You Use Laxatives for Weight Loss?
Many people search for laxatives as a weight loss solution, but they're not an effective or safe approach to losing weight. Laxatives work on your bowels, not on body fat — any weight loss is temporary water and stool weight, not genuine fat loss. The NHS and health experts warn against using laxatives for weight management because they can lead to dehydration, nutrient deficiencies, and dependency. If you're looking for sustainable weight management in the UK, evidence-based approaches like dietary changes, increased physical activity, and prescription medications (where appropriate) are far more effective.
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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.
Why Laxatives Don't Work for Weight Loss
Laxatives only affect bowel movements — they do not reduce body fat or change how your body processes calories. Any weight loss you see after taking a laxative is from loss of water and stool, which returns within 24–48 hours of normal eating and drinking. This creates a false sense of progress and can lead to repeated misuse.
Health risks of laxative misuse for weight loss include:
- Severe dehydration and electrolyte imbalances
- Dependency and loss of normal bowel function
- Malabsorption of nutrients (calcium, iron, vitamins)
- Abdominal pain and cramping
- Weakened colon muscles over time
Using laxatives as a weight loss method is not recommended by the NHS, NICE, or any major health organisation. It's a form of disordered eating behaviour and can be dangerous, especially if combined with other restrictive practices.
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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.
Evidence-Based Weight Management Alternatives
Instead of laxatives, the NHS recommends sustainable approaches to weight management in the UK: reducing calorie intake (aiming for a deficit of around 500 kcal per day for approximately 0.5 kg weekly loss), increasing physical activity, and eating a balanced diet rich in vegetables and whole grains.
For eligible adults, prescription weight loss medication like GLP-1 injections (Wegovy or Mounjaro) offer evidence-based support. These work by reducing appetite and helping you feel fuller on smaller meals — not by forcing water loss. Clinical trials showed semaglutide (Wegovy) helped participants lose an average of around 15% body weight, though results vary. Your GP can discuss whether weight loss medication is appropriate for your individual 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 do laxatives cause quick weight loss if they don't burn fat?
Laxatives trigger bowel movements that remove stool and water from your body temporarily. This creates gradual weight management on the scales, but it's not fat loss. The weight returns within 1–2 days as you eat and drink normally. There's no actual change to body composition or calorie balance.
Is it safe to use laxatives occasionally for weight loss?
No. Even occasional misuse of laxatives for weight loss is unsafe. It can disrupt your bowel health, cause dehydration, and establish unhealthy patterns. If you're struggling with weight or tempted by laxative misuse, speak to your GP — they can discuss safe, effective options including behaviour support and prescription treatments.
What's the difference between laxatives and GLP-1 weight loss injections?
Laxatives only affect bowel movements; GLP-1 injections (like Wegovy) work on your appetite and metabolism. GLP-1 helps you eat fewer calories naturally by reducing hunger and cravings. It creates genuine fat loss when combined with a reduced-calorie diet, not just temporary water loss. GLP-1 medications are prescription-only.
Can I use our GLP-1 weight loss calculator to estimate results?
Yes. Our free weight loss calculator can help you project potential weight loss with prescription GLP-1 medication at different doses. This gives you a realistic picture of what evidence-based weight management might achieve — far more effective than laxatives. Your GP or prescriber can discuss whether you're eligible.
What should I do if I've been using laxatives to lose weight?
Stop using them and speak to your GP. You may need electrolyte testing and advice on reestablishing normal bowel function. Your GP can also discuss safe, sustainable weight management strategies tailored to you — including lifestyle changes and prescription options if appropriate. Support is available.
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.