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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How Can Do Weight Loss With Medication in the UK
Weight loss is achievable through several methods, and for eligible adults in the UK, prescription medication can be an effective tool alongside diet and exercise. If you're struggling with weight management, understanding your options is the first step. This guide explains the prescription weight loss medications available through the NHS and private healthcare, who can access them, and how to find out if you're eligible. We'll also help you start a conversation with your GP about the right approach for your health goals.
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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 Weight Loss Medications
Three prescription medications are licensed in the UK specifically for weight management in adults. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist, helping regulate appetite and support feeling fuller after meals. Clinical trials showed adults lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. Wegovy (semaglutide) is also a once-weekly GLP-1 injection, with clinical trial data showing approximately 15% average body weight loss. Saxenda (liraglutide) is a daily GLP-1 injection with similar mechanisms. All three are prescription-only and require a clinical assessment before being prescribed.
Eligibility typically requires a BMI of 30 or above, or 27 or above if you have 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 due to higher health risks at lower weights. These medications work best alongside a reduced-calorie diet and increased physical activity—they are not replacements for lifestyle changes. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to check where you currently stand on the NHS scale.
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 in the UK
NHS access: You can be referred to a specialist tier 3 or tier 4 weight management service by your GP. NICE has approved tirzepatide (Mounjaro) for NHS use, and availability is expanding across regions, though waiting times and access vary significantly by integrated care board (ICB). If your GP thinks you might be eligible, they can refer you for specialist assessment.
Private access: Prescription weight loss medications are available through GPhC-registered online prescribing services following an online clinical consultation. You don't need an NHS referral, and treatment can usually start within days rather than months. Costs vary by dose and provider, typically ranging from £129–£320 per month.
The first step is always a conversation with your GP. They can assess your health, discuss whether medication might be appropriate, explain local NHS options, and help you decide the best route forward. Track your progress with our free progress tracker once you've started any weight management approach.
- 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.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27 or above with a weight-related health condition like type 2 diabetes or high blood pressure. Use our BMI calculator to check your current BMI. South Asian, Chinese, Black African, and Black Caribbean adults may have lower thresholds. Your GP can assess your individual eligibility.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy over several months. However, individual results vary significantly based on dose, lifestyle changes, and personal factors. Our GLP-1 weight loss calculator can help you estimate potential outcomes.
What's the difference between NHS and private weight loss medication in the UK?
NHS access involves referral to specialist services with variable waiting times depending on your region. Private access is through online prescribing services and typically faster, but involves cost. Both require clinical assessment. Your GP can help you explore which route is right for you.
Do I need to change my diet and exercise if I take weight loss medication?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. They support weight loss by helping regulate appetite, but lifestyle changes are essential for sustainable results and long-term health benefits.
What should I do if I think weight loss medication might help me?
Start by talking to your GP. They can assess your health, discuss whether medication is appropriate, explain NHS options in your area, and refer you to specialist services if needed. They can also advise on private options if NHS waiting times are lengthy.
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.