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
Fiber Supplements and Weight Loss in the UK
Fiber supplements are sometimes promoted for weight loss, but evidence for their standalone effect is limited. While dietary fiber plays an important role in healthy eating and digestion, adults seeking significant weight management support in the UK may be eligible for prescription weight loss medication. This guide explains what fiber does, how it compares to clinical weight loss options, and how to find out if you qualify for NHS or private prescription treatment.
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 Options
For adults with a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions, three prescription-only medications are licensed in the UK for weight management:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist, once-weekly injection, typical average weight loss 15–21% of body weight in clinical trials
- Wegovy (semaglutide) — GLP-1 receptor agonist, once-weekly injection, average weight loss approximately 15% in clinical trials
- Saxenda (liraglutide) — GLP-1 receptor agonist, once-daily injection
These prescription weight loss medications work alongside dietary changes and increased physical activity. Unlike supplements, they have been rigorously tested in clinical trials and their effects on appetite regulation and weight loss are clinically proven. Individual results vary, but they offer significantly more substantial support than dietary supplements alone. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
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 Medication
In the UK, prescription weight loss medication is available through two main routes. NHS access is through specialist tier 3 weight management services, typically requiring referral from your GP. Waiting times vary significantly by region, and availability is not uniform across all areas. Private access is available through GPhC-registered online prescribing services, following an online clinical assessment — no NHS referral required.
To find out if you're eligible, start by checking your BMI using our free BMI calculator above. If your BMI suggests you may qualify, speak with your GP about NHS options in your area, or explore private prescribing services. A licensed prescriber will assess your individual health and suitability before any prescription is issued.
- 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.
Do fiber supplements help with weight loss?
Fiber supplements may support appetite control and digestion as part of a healthy diet, but evidence for significant standalone weight loss is limited. They work best alongside whole dietary changes. For substantial weight management support, prescription medication offers more clinically robust results.
What's the difference between fiber supplements and prescription weight loss injections?
Fiber supplements are over-the-counter products affecting digestion. Prescription weight loss medications like Mounjaro and Wegovy are prescription-only drugs that regulate hunger hormones and appetite regulation. They have been extensively tested in clinical trials and produce measurable weight loss results — far more substantial than supplements.
Am I eligible for NHS weight loss medication?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with a weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. Speak with your GP about referral to a specialist weight management service in your area. Availability varies by region.
Can I get prescription weight loss medication privately without NHS waiting?
Yes. Private prescription weight loss medication is available through GPhC-registered online prescribing services. You complete an online clinical assessment, and if suitable, a UK-licensed prescriber issues a prescription. This typically bypasses NHS waiting times, though you pay privately.
Which prescription weight loss medication is most effective?
In clinical trials, Mounjaro (tirzepatide) showed slightly higher average weight loss (15–21%) than Wegovy (around 15%), though results vary significantly between individuals. A prescriber will assess which is most appropriate for your health profile and circumstances. Both are prescription-only and require clinical assessment.
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.