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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Weight Loss Medication in the UK — What You Need to Know
If you're looking for weight management UK support through prescription medication, there are several licensed options available to eligible adults. The NHS and private healthcare both offer access to approved medications like Mounjaro and Wegovy, alongside lifestyle changes. Understanding your eligibility, how these medications work, and whether NHS or private access is right for you is the first step toward effective weight loss management. This guide covers everything you need to know about prescription weight loss medication options 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-Approved Weight Loss Medications
Three prescription-only weight loss medications are currently licensed in the UK for adults with obesity or overweight with weight-related health conditions:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, injected once weekly. In clinical trials, it helped participants lose an average of 15–21% of their body weight alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, injected once weekly. Clinical evidence showed an average weight loss of around 15% body weight over 68 weeks.
- Saxenda (liraglutide) — A GLP-1 agonist, injected daily. Results vary by individual. All three are prescription-only and require a clinical assessment to determine suitability.
Eligibility typically includes adults with 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. Our free GLP-1 weight loss calculator can help you explore potential outcomes with these medications.
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 — Finding Your Pathway
NHS access: Weight loss medication through the NHS is available via specialist tier 3 weight management services, usually accessed through a GP referral. However, NHS availability varies significantly by region, and waiting lists can be lengthy in many areas. Your GP can advise whether you meet local criteria and refer you for assessment.
Private access: Private online prescribing services offer faster access without NHS referral. A UK-licensed prescriber will assess your eligibility through a clinical consultation. This pathway is available to most eligible adults, though costs vary by dose and provider. Whichever route you choose, prescription weight loss medication is always combined with dietary changes and increased physical activity for best results. Check your BMI and health status using our free BMI calculator to understand your starting point.
- 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.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro showed slightly higher average weight loss in clinical trials (~15–21% vs ~15%), but individual results vary significantly. Both are injected once weekly and require prescription and clinical assessment.
Who is eligible for prescription weight loss medication in the UK?
Generally, adults with a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. Your GP or a licensed prescriber can assess your individual eligibility.
How long does it take to see weight loss results?
Weight loss typically begins within the first few weeks on prescription medication, though results vary. Most significant changes occur over 3–6 months. Clinical trials measured results over 15–20 weeks. Results depend on the dose, individual metabolism, adherence to a reduced-calorie diet, and increased physical activity.
Can I get weight loss medication through the NHS without a long wait?
NHS access depends on your local Integrated Care Board (ICB) and regional availability. Many areas have long waiting lists for specialist weight management services. Your GP can check local provision. Private online prescribing offers faster access but involves a cost. Both pathways require a proper clinical assessment.
Do these medications work without diet and exercise changes?
No. All UK-licensed weight loss medications are prescribed alongside a reduced-calorie diet and increased physical activity. The medication supports appetite control and metabolism, but sustainable weight loss requires lifestyle changes. Our progress tracker can help you log dietary and activity changes alongside any medication you may be prescribed.
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.