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
Supplements and Weight Loss — What Works in the UK
Many people turn to weight loss supplements hoping for quick results, but the evidence for over-the-counter supplements is limited. If you're struggling with your weight, prescription weight management medication available in the UK may be more effective. This guide explains the difference between supplements and licensed medications, who is eligible for prescription options, and how to start a conversation with your GP about weight loss support.
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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 Weight Loss Medications
If you're interested in prescription weight loss medication in the UK, three options are currently licensed for weight management:
- Mounjaro (tirzepatide) — A once-weekly injection that works by activating GIP and GLP-1 hormone pathways. Clinical trials showed participants lost an average of 15–21% of their body weight alongside diet and exercise changes.
- Wegovy (semaglutide) — A once-weekly GLP-1 injection. In clinical trials, participants lost approximately 15% of their body weight on average at the highest dose.
- Saxenda (liraglutide) — A daily GLP-1 injection, though less commonly prescribed than Mounjaro and Wegovy.
All three are prescription-only and require a clinical assessment to determine eligibility. Results vary between individuals, and these medications work best when combined with reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator to estimate potential results 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 Access and Getting Started
In the UK, you can access prescription weight loss medication through two routes: NHS specialist services or private prescribing. NHS access is through tier 3 specialist weight management services — typically requiring a GP referral. Availability varies by region, and waiting lists can be lengthy in many areas.
Privately, you can access medication through registered online prescribers following a clinical assessment, without NHS referral. To find out if you're eligible, calculate your BMI using our free BMI calculator — adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure, may qualify. Your first step is a conversation with your GP about your weight loss goals and whether prescription medication might be appropriate for you.
- 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.
Are weight loss supplements effective compared to prescription medication?
Most over-the-counter supplements have limited clinical evidence for weight loss. Prescription GLP-1 medications like Mounjaro and Wegovy have been tested in large clinical trials showing average weight losses of 15–21%. Always discuss options with your GP to find the right approach for your health.
Who is eligible for prescription weight loss medication on the NHS?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Requirements vary by region. Your GP can assess your individual eligibility and refer you to specialist weight management services if appropriate.
Can I get prescription weight loss medication without an NHS referral?
Yes. You can access prescription weight loss medication privately through registered online prescribers in the UK. They'll conduct a clinical assessment to confirm eligibility. This route doesn't require an NHS referral but involves private costs.
Do prescription weight loss injections work without diet and exercise changes?
Prescription medications like Mounjaro and Wegovy are most effective when combined with reduced-calorie diet and increased physical activity. Clinical trials showed weight loss achieved alongside lifestyle changes. Medication supports your efforts — it's not a replacement for them.
How do I know if weight loss medication is right for me?
Start by speaking with your GP about your weight loss goals, health conditions, and any concerns. Your GP can assess your BMI, discuss medication options, and determine whether prescription treatment is appropriate. You can also use our free weight loss calculator to explore potential outcomes at different doses.
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.