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
Laxatives and Weight Loss — What You Need to Know
Laxatives are sometimes discussed online as a weight loss tool, but they don't actually help with sustainable weight management. In fact, using laxatives to lose weight can be harmful and may lead to dependency. If you're looking for effective weight loss support in the UK, there are evidence-based prescription options available for eligible adults. This guide explains why laxatives aren't a safe choice and what actually works for lasting weight management.
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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.
UK-Licensed Prescription Weight Management Options
If you're struggling with weight management, the NHS and private clinicians in the UK can offer prescription medications that are clinically proven to support weight loss. These include Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist, and Wegovy (semaglutide), a GLP-1 agonist. Both are once-weekly injections licensed for adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions.
Clinical trials show Mounjaro helped participants lose an average of 15–21% of their body weight, whilst Wegovy supported approximately clinically studied weight loss — though individual results vary significantly. Saxenda (liraglutide) is also available as a daily injection option. These medications work by helping regulate appetite and supporting you to feel fuller after smaller meals, alongside a reduced-calorie diet 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 Access or Private Prescription — Which Is Right for You?
Accessing prescription weight loss medication in the UK depends on your circumstances. Through the NHS, you can be referred to a specialist tier 3 or tier 4 weight management service by your GP — though waiting lists vary significantly by region and availability can be limited. Private prescribers offer faster access through online consultations with UK-licensed doctors, with dispensing through GPhC-registered pharmacies.
Before any prescription, you'll have a clinical assessment to check eligibility. Your GP can discuss which route is suitable for you and whether prescription medication is appropriate based on your health, BMI, and any existing conditions. Use our free BMI calculator to check your starting point, then speak with your healthcare provider about options for sustainable weight management.
- 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 aren't laxatives a safe way to lose weight?
Laxatives don't lead to real fat loss — they only cause temporary water loss and can damage your digestive system with regular use. They can lead to dependency, electrolyte imbalances, and serious complications like dehydration. Safe weight loss comes from calorie deficit combined with lifestyle changes or, for eligible adults, prescription medication under clinical supervision.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are GLP-1-based medications, but Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), whilst Wegovy (semaglutide) activates GLP-1 only. Mounjaro doses range up to 15mg weekly, Wegovy up to 2.4mg weekly. Clinical trials showed slightly higher average weight loss with Mounjaro, though results vary between individuals. Both require prescription and clinical assessment.
How do I know if I'm eligible for NHS weight loss medication?
Generally, you're eligible if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). For South Asian, Chinese, or Black African/Caribbean heritage, lower BMI thresholds apply. Your GP can assess your eligibility and refer you to a specialist weight management service.
How quickly does prescription weight loss medication work?
Results typically become noticeable within 4–6 weeks but continue building over several months. Maximum benefit is usually seen after 12–16 weeks of treatment. Doses are increased gradually over weeks or months to minimise side effects. Weight loss happens alongside a reduced-calorie diet and increased physical activity — medication supports these changes, not replaces them.
Can I get prescription weight loss medication privately if the NHS waiting list is too long?
Yes. Private online clinics can offer faster access through UK-licensed prescribers following an online consultation. Prescriptions are dispensed by GPhC-registered pharmacies. Costs vary by dose and provider (typically £150–£320 monthly). Always ensure the prescriber is UK-licensed and the pharmacy is registered with the General Pharmaceutical Council for safety and legitimacy.
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.