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
Weight Loss Medication Available in the UK
While body firming lotions may temporarily improve skin appearance, sustainable weight management requires a comprehensive approach. For adults struggling with excess weight, prescription weight loss medications are now available through the NHS and private prescribers in the UK. These evidence-based options work alongside diet and physical activity to help support weight loss. Our free BMI calculator can help you understand where you stand, and we'll explain your medication options and eligibility.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Loss Options
Three prescription medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 and GIP/GLP-1 receptor agonist injections that work by helping regulate appetite and blood sugar.
- Mounjaro — dual GIP and GLP-1 agonist, once-weekly injection, doses from 2.5mg to 15mg. Clinical trials showed average weight loss of 15–21% body weight.
- Wegovy — GLP-1 agonist, once-weekly injection, maximum dose 2.4mg. Clinical trials showed average weight loss around 15% body weight.
- Saxenda — GLP-1 agonist, once-daily injection, maximum dose 3mg. Similar effectiveness to Wegovy.
All three are prescription-only and require clinical assessment to confirm eligibility. Try our GLP-1 weight loss calculator to estimate potential outcomes 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.
Who Is Eligible and How to Access Treatment
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Access in the UK comes through two routes: NHS specialist weight management services (via GP referral, often with waiting lists) or private online prescribing (following an online clinical assessment with a UK-licensed prescriber). Regional variation exists across NHS services. Your GP can assess whether nhs weight loss medication is right for you and refer you to specialist services if appropriate, or you can explore private options independently. Use our BMI calculator to check your starting point, then speak with your GP about prescription weight loss options.
- 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 prescription weight loss injections available on the NHS?
Yes, Mounjaro and Wegovy are now approved by NICE for NHS use within specialist tier 3 weight management services. Access varies by region and availability. Your GP can refer you to specialist services, though waiting lists may be lengthy in some areas. Private access is also available without NHS referral.
What is the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 agonist and tends to produce slightly higher average weight loss (15–21% body weight). Wegovy is a GLP-1-only agonist with average weight loss around 15% body weight. Both are once-weekly injections. Clinical trials show both are effective; individual results vary significantly.
How much weight can I lose with these medications?
Clinical trial averages range from 15–clinically studied weight loss over 12–18 months, depending on the medication and dose. However, individual results vary considerably. Weight loss works best alongside a reduced-calorie diet and increased physical activity. Use our GLP-1 weight loss calculator to estimate potential outcomes.
Do I need a prescription to access weight loss medication in the UK?
Yes, all UK-licensed weight loss medications are prescription-only. You cannot buy them over-the-counter. Access is through either NHS specialist services (via GP referral) or private prescribers following an online clinical assessment. Both pathways require a valid prescription.
What is my eligibility for weight loss medication?
Eligibility typically requires BMI 30 or above, or BMI 27–29.9 with weight-related health conditions (diabetes, hypertension, sleep apnoea, cardiovascular disease). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply. Your GP or a licensed prescriber will assess your individual eligibility.
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.