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
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Does Glucomannan Actually Help With Weight Loss?
Glucomannan is a natural soluble fibre supplement that many people in the UK use hoping to lose weight. It absorbs water in your stomach and may help you feel fuller for longer. However, the evidence for significant weight loss is modest — it's not a weight loss medication like prescription options. Before and after stories circulate online, but clinical trials show much smaller, more realistic results. This guide explains how glucomannan actually works, what research shows, and how it compares to evidence-based weight management approaches supported by the NHS.
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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.
How Glucomannan Works and What Research Shows
Glucomannan is a soluble dietary fibre extracted from the konjac plant root. When mixed with water, it absorbs moisture and expands in your stomach, creating a feeling of fullness. This may help reduce appetite and food intake in some people. Clinical trials show modest results: glucomannan typically supports weight loss of around 2.5 kg over 8–12 weeks when combined with a calorie-restricted diet — far less dramatic than before and after stories suggest. The fibre also has other potential benefits including supporting cholesterol levels and gut health. However, glucomannan alone does not produce significant weight loss without dietary changes. You must create a calorie deficit through diet and exercise for any supplement to have a meaningful effect. The NHS emphasises that sustainable weight loss of 0.5–1 kg per week requires reduced-calorie eating and increased physical activity — glucomannan is only a minor supporting tool, not a solution on its own. Always take glucomannan with plenty of water to avoid digestive obstruction.
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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.
Glucomannan vs Prescription Weight Loss Options
If you're looking at before and after comparisons, it's worth understanding that prescription weight loss medications produce significantly larger results. Medications like Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1 or dual GIP/GLP-1 receptor agonists licensed by the MHRA for weight management in UK adults. Clinical trials show these support average weight loss of 15–21% of body weight — substantially more than glucomannan's modest 2–3% effect. These are prescription-only and require clinical assessment, but they're backed by large clinical trials. Glucomannan, by contrast, is an over-the-counter supplement with much weaker evidence. Both approaches work best alongside diet and exercise. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions, ask your GP about NHS weight management pathways or specialist referral. Use our free BMI calculator above to assess your current status and our GLP-1 weight loss calculator to see projected outcomes with evidence-based medication options.
- 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 before and after photos of glucomannan actually represent real results?
Most dramatic before and after images involve significant lifestyle changes alongside glucomannan — diet, exercise, and often medical supervision. Glucomannan alone produces modest results (typically 2–3 kg over 12 weeks). Online photos often show results from calorie restriction, not from the supplement itself. Clinical trials are more reliable than social media claims.
Is glucomannan safe to take long-term?
Glucomannan is generally safe when taken with adequate water. However, it can cause bloating, constipation, or digestive discomfort initially. It must be taken with at least 250 ml of water to avoid potential oesophageal obstruction. Always check with your GP before starting, especially if you take oral medications — glucomannan can affect their absorption.
Can I use glucomannan instead of seeing my GP about weight loss?
Glucomannan is a supplement, not a medical treatment. If you're overweight or obese (BMI 25+), your GP can assess your health and discuss evidence-based options including NHS weight management services, prescription medication, or lifestyle support. Supplements should complement, not replace, professional guidance.
How does glucomannan compare to GLP-1 weight loss injections?
Glucomannan is an over-the-counter fibre supplement with small clinical effects (2–3 kg loss). GLP-1 medications like Wegovy are prescription-only and produce much larger results (15% body weight or more in trials). GLP-1 medications require clinical assessment and MHRA approval, while glucomannan does not. Results vary individually in both cases.
Why don't before and after results match what I see online?
Online images often omit important details: calorie counting, exercise, medical support, and the timeframe over which results occurred. Additionally, people are more likely to share dramatic results than modest ones, creating unrealistic expectations. Clinical trial data (not social media) provides the most honest picture of what to expect.
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.