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 Operation: UK Prescription Medication Options
When people search for "weight loss operation," they're often exploring all available options for managing excess weight. In the UK, prescription weight management medications offer an alternative approach to surgery. These medications, known as GLP-1 receptor agonists, are available through the NHS or private prescribing if you meet eligibility criteria. This guide explains what's available, who can access treatment, and how to have the conversation with your GP about whether prescription weight loss medication might be right for you.
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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
Three prescription medications are currently licensed for weight management in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist taken once weekly. In clinical trials, it helped participants lose an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. Wegovy (semaglutide) is a GLP-1 receptor agonist also taken once weekly, with trial data showing average weight loss of approximately 15% over 68 weeks. Saxenda (liraglutide) is a daily GLP-1 injection option.
All three are prescription-only medicines requiring clinical assessment before dispensing. Eligibility typically includes adults with a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. These medications work alongside lifestyle changes—reduced-calorie diet and increased physical activity—not instead of them.
Try our free GLP-1 weight loss calculator to estimate potential weight loss at different doses, and use our BMI calculator to check your current BMI and eligibility status.
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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 Path to Treatment
NHS access: Weight loss medications are available through tier 3 specialist weight management services. You'll typically need a referral from your GP, and assessment is conducted by a multidisciplinary team. However, NHS availability varies significantly by region—some areas have long waiting lists, whilst others have limited provision. Specialist services can take several months to assess and begin treatment.
Private access: GLP-1 medications are available through GPhC-registered online pharmacies following a consultation with a UK-licensed prescriber. This route doesn't require NHS referral and is typically faster, though it involves direct costs ranging from approximately £129–£320 per month depending on dose and provider. Both routes require a valid prescription—no medication is dispensed without clinical assessment.
Start by speaking with your GP about weight management options. They can assess your individual health, discuss what might be suitable, and either refer you to NHS services or advise you on private options. Our weight converter and progress tracker can help you monitor changes over time.
- 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.
Is prescription weight loss medication the same as weight loss surgery?
No. Prescription weight management medications like Mounjaro and Wegovy are injections that reduce appetite and support feeling fuller. Surgery (such as gastric bypass) is a more invasive intervention. Many people try medication first before considering surgery, as it's non-surgical and can be stopped if needed.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight, but individual results vary significantly. Some people lose more, others less. Weight loss depends on the medication, your dose, adherence, diet, and activity level. Your prescriber can discuss realistic expectations for your situation.
Do I need a referral from my GP to access these medications?
For NHS access, yes—you'll typically need a GP referral to specialist weight management services. For private prescribing, no referral is needed, though speaking with your GP is advisable. Your GP can discuss options, check your eligibility, and help you decide the best route for you.
Are these medications available on the NHS?
Yes, Mounjaro and Wegovy are available through NHS specialist tier 3 weight management services, though regional availability varies and waiting lists can be long. Not all areas offer equal access. Your GP can advise what's available in your region.
What happens if I stop taking the medication?
Weight loss from these medications is typically not permanent. If you stop, your appetite tends to return and weight may gradually increase again over time. For this reason, treatment is often ongoing for people who benefit. Your prescriber will discuss long-term plans with you.
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.