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
OTC Weight Loss Supplements and Prescription Alternatives in the UK
Over-the-counter weight loss supplements are widely available, but evidence for their effectiveness is limited. If you're looking for weight management solutions in the UK, prescription medications offer a clinically proven alternative. This guide explains both options and helps you understand which might be suitable for your situation, plus how to check your eligibility for NHS or private prescription weight loss treatment.
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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 have a BMI of 30 or above, or 27 or above with weight-related health conditions, you may be eligible for prescription weight loss medication in the UK. Three medications are currently licensed for weight management:
- Mounjaro (tirzepatide) — a once-weekly GLP-1 and GIP receptor agonist injection. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks alongside reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a once-weekly GLP-1 receptor agonist injection. Clinical evidence suggests average weight loss of around 15% of body weight.
- Saxenda (liraglutide) — a daily GLP-1 injection. Evidence supports modest weight loss alongside lifestyle changes.
All three are prescription-only and require clinical assessment before being prescribed. Try 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 Access vs Private Prescription Routes
In the UK, prescription weight loss medication is available through two routes. NHS access is through specialist tier 3 weight management services — your GP can refer you, though waiting lists vary significantly by region. Private access is through GPhC-registered online prescribers following an online clinical assessment, available without NHS referral.
Check your eligibility using our free BMI calculator above. If your BMI suggests you may qualify, discuss options with your GP or consider a private clinical assessment. Either route requires a prescription from a licensed UK prescriber — prescription weight loss medication is not available over-the-counter.
- 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 OTC weight loss supplements regulated in the UK?
OTC supplements are regulated by the Food Standards Authority and must not make disease claims, but evidence for weight loss effectiveness is often limited. Prescription medications like Mounjaro and Wegovy undergo rigorous clinical trials and MHRA approval, offering stronger evidence of effectiveness for eligible adults.
Who is eligible for prescription weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Lower BMI thresholds may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess your individual eligibility.
What's the difference between Mounjaro and Wegovy for weight management?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21% vs 15%), though individual results vary significantly. Both are once-weekly injections and require prescription.
How quickly will I lose weight with prescription weight loss medication?
Safe, sustainable weight loss is typically 0.5–1 kg per week. Clinical trials showed average losses of 15–21% of body weight over 68–72 weeks, but results vary based on dose, adherence, diet, and physical activity. Weight loss medication works best alongside a reduced-calorie diet and increased movement.
Can I get prescription weight loss medication privately without NHS referral?
Yes. Private GPhC-registered online prescribers can assess you for prescription weight loss medication following an online consultation. This route bypasses NHS waiting lists but involves private costs. Your GP can also discuss both NHS and private options with you to help decide what's best for your situation.
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.