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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Good Weight Loss Supplements: UK Prescription Options
When searching for good weight loss supplements, many people don't realise that the most effective options available in the UK are prescription medications, not over-the-counter supplements. If you're looking to manage your weight, prescription weight loss injections like Mounjaro and Wegovy are clinically proven options available through the NHS or private prescribing. This guide explains what's available, who's eligible, and how to access these medications in the UK.
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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 Loss Medications
The term "weight loss supplements" often refers to unproven products, but the most effective, evidence-backed options for weight management in the UK are prescription medications. Three main options are currently licensed for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, alongside diet and exercise changes.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. In clinical trials, participants achieved approximately 15% average body weight loss at the maximum dose (2.4 mg).
- Saxenda (liraglutide) — a daily GLP-1 injection, approved for weight management in the UK. Average weight loss is typically 5–10% of body weight.
All three are prescription-only medicines requiring a clinical assessment. Individual results vary significantly, and these medications work best alongside a reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different dose levels.
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: How to Get Weight Loss Medication
NHS route: Prescription weight loss medication is available through NHS specialist tier 3 weight management services, but access is limited and varies significantly by region. Referral from your GP is required, and waiting lists can be lengthy in many areas. Not all NHS integrated care boards offer these medications.
Private route: You can access prescription weight loss medication through private online consultations with UK-licensed prescribers. Following a clinical assessment, a prescription may be issued if you meet the eligibility criteria. This option is available without an NHS referral.
Check your eligibility: Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure, may be eligible. Use our free BMI calculator above to check your personal BMI, then speak with your GP or a licensed prescriber about your 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.
Are over-the-counter weight loss supplements effective?
Most over-the-counter supplements lack strong clinical evidence for weight loss. Prescription medications like Mounjaro and Wegovy have robust clinical trial data and are significantly more effective. Always speak with your GP before trying any supplement or medication.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1-only medication. Mounjaro showed slightly higher average weight loss in clinical trials (15–21% vs 15%), but individual results vary. Both are once-weekly injections approved in the UK for weight management.
Can I get prescription weight loss medication on the NHS?
Yes, but access is limited. You need referral to a specialist NHS tier 3 weight management service, and availability varies by region. Waiting lists can be several months. Private prescribing offers faster access without an NHS referral, following a clinical assessment.
What makes someone eligible for prescription weight loss medication in the UK?
Generally, you're eligible if your BMI is 30 or above, or 27 or above with a weight-related health condition (diabetes, high blood pressure, sleep apnoea, etc.). Adults of South Asian, Black African, or Black Caribbean heritage may be eligible at slightly lower BMI thresholds. A prescriber will assess your individual situation.
How much weight will I lose on Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% for Mounjaro and approximately 15% for Wegovy, but individual results vary considerably. Some people lose less, others more. Weight loss is most effective when combined with a reduced-calorie diet and increased physical activity. Results depend on your starting weight, dose, adherence, and lifestyle changes.
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.