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 Reduction Medication in the UK
Weight reduction medication is an evidence-based treatment option available to eligible UK adults struggling with excess weight. The NHS and NICE now recommend prescription weight management medications alongside lifestyle changes for people with obesity or overweight with health complications. This guide explains what these medications are, how they work, UK eligibility criteria, and how to access them through the NHS or private prescribing.
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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.
How Weight Reduction Medications Work in the UK
Weight reduction medications approved in the UK include GLP-1 receptor agonists (Wegovy, Saxenda) and the newer dual GIP/GLP-1 medication Mounjaro. These work by mimicking natural hormones that regulate appetite and food intake.
GLP-1 medications activate pathways in the brain that signal fullness, reducing hunger and cravings. They also slow how quickly food leaves the stomach, helping you feel satisfied with smaller portions. Unlike older weight loss drugs, these medications are based on hormones naturally produced in your gut after eating.
- Wegovy (semaglutide): Once-weekly injection, GLP-1 agonist
- Mounjaro (tirzepatide): Once-weekly injection, dual GIP/GLP-1 agonist
- Saxenda (liraglutide): Once-daily injection, GLP-1 agonist
Clinical trials show these medications help people lose an average of 15–21% of body weight when combined with healthy eating and physical activity. Individual results vary significantly, and weight reduction medication is most effective alongside lifestyle changes, not as a replacement for them.
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.
UK Eligibility and How to Access Weight Reduction Medication
In the UK, weight reduction medications are available through two routes: NHS specialist services and private prescribing. NHS access requires referral to a tier 3 weight management service, typically from your GP. NICE guidance recommends these medications for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease.
Private prescribing is available without NHS referral through GPhC-registered online pharmacies, following an online clinical assessment with a UK-licensed prescriber. Access and waiting times vary significantly by region.
Use our free BMI calculator above to check if you may meet eligibility criteria, then discuss with your GP or a licensed prescriber about whether weight reduction medication is appropriate for your circumstances.
Before starting any weight reduction medication, expect a thorough health assessment. Your prescriber will review your medical history, current medications, and any existing health conditions. All prescription weight management medications require ongoing monitoring to track progress and manage any side effects.
Common side effects include nausea, diarrhoea, and reduced appetite — these often ease over time as your body adjusts. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder issues. Our progress tracker can help you log your weight loss journey and monitor how you feel as treatment progresses.
Remember that weight reduction medication works best alongside a reduced-calorie, balanced diet and regular physical activity. Your GP or prescriber will discuss realistic expectations and ensure you receive personalised support throughout treatment.
- 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 reduction medications available on the NHS in the UK?
Yes. NICE guidelines recommend weight management medications including Mounjaro, Wegovy, and Saxenda for eligible adults. Access is through NHS tier 3 specialist weight management services, typically by referral from your GP. Availability and waiting times vary by region and local commissioning decisions.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist with a maximum dose of 15mg weekly. Wegovy (semaglutide) is a GLP-1 agonist only, with a maximum dose of 2.4mg weekly. Both are once-weekly injections. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but individual results vary. Your prescriber will advise which is more suitable for you.
How much weight can I expect to lose with weight reduction medication?
Clinical trials show average weight loss of 15–21% of body weight over approximately 68–72 weeks, alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly — some people lose more, others less. Weight reduction medication is a tool to support healthy lifestyle changes, not a assures of specific weight loss.
What are the main side effects of weight reduction medication?
Very common side effects include nausea, diarrhoea, constipation, and stomach pain — these often improve as your body adjusts. Less common side effects include fatigue, dizziness, and injection site reactions. Serious side effects are rare but include severe stomach pain suggesting pancreatitis. Always inform your prescriber of any concerns.
Can I get weight reduction medication privately if I'm not eligible for NHS treatment?
Yes. Private weight reduction medications are available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. You don't need an NHS referral. Costs vary depending on the medication and dose, typically ranging from £129–£320+ per month. Always verify the pharmacy is GPhC-registered before purchasing.
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.