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 Motivation and Prescription Options in the UK
Finding motivation for weight loss is personal, but in the UK today, you have more support options than ever before. If you're struggling with excess weight, prescription medications like Mounjaro and Wegovy are now available through both NHS specialist services and private prescribing. This guide covers UK-licensed weight management options, eligibility criteria, and how prescription treatment can support your journey alongside lifestyle changes. Use our free BMI calculator and GLP-1 weight loss calculator to understand your current position and explore what results others have achieved.
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 Medications
Three medications are currently licensed in the UK for weight management in adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy and Saxenda are GLP-1 agonists only. In clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight, and Wegovy around 15%, though individual results vary significantly.
Eligibility for prescription weight loss medication in the UK includes adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at slightly lower BMI thresholds due to higher health risks at those levels.
All three medications are prescription-only and require a clinical assessment before being prescribed. They work alongside a reduced-calorie diet and increased physical activity — medication alone is not a complete solution.
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 Access vs Private Prescribing in the UK
NHS access to weight management injections is through specialist tier 3 or tier 4 weight management services, usually accessed via GP referral. Availability varies significantly by region, and waiting lists can be lengthy in many areas. Your GP can assess whether referral is appropriate for you.
Private prescribing is available through GPhC-registered online pharmacies following a clinical consultation. This route doesn't require NHS referral and offers faster access, though costs typically range from £129–£320 per month depending on dose. Whichever route you choose, speak to your GP first about whether medication is suitable for your health profile. Use our free progress tracker to monitor your weight loss journey once you've started 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.
What BMI do I need to qualify for weight loss medication in the UK?
You may be eligible if your BMI is 30 or above, or 27–29.9 if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, or Black Caribbean adults may qualify at BMI 27.5 or above. Calculate your BMI using our free tool to find out where you stand.
Can I get Mounjaro or Wegovy through the NHS?
Yes, both are available through NHS specialist weight management services, typically accessed via GP referral. However, availability and waiting times vary significantly by region (ICB). Your GP can advise whether you're eligible and discuss the referral process. Private prescribing is also available without NHS referral.
How much weight can I expect to lose with these medications?
Clinical trials showed average weight loss of 15–21% with Mounjaro and around 15% with Wegovy over approximately 68–72 weeks, alongside diet and exercise. However, individual results vary significantly — some lose more, some less. Results depend on your starting weight, adherence, diet, and activity level.
Are there side effects with weight loss injections?
Yes. Common side effects include nausea, diarrhoea, vomiting, and constipation, especially when starting or increasing doses. Most side effects are mild and improve over time. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder issues. Your prescriber will discuss risks and benefits.
How should I start the conversation with my GP about weight loss medication?
Book a routine appointment and explain that you're interested in exploring all weight management options, including prescription medication. Share your BMI (use our free calculator), any weight-related health conditions, and what lifestyle changes you've already tried. Your GP can assess eligibility and discuss NHS or private options suitable for 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.