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
Free Weight Loss Planner — UK Medication Options
A free weight loss planner helps you map your weight management journey, whether through lifestyle changes alone or with prescription support. If you're looking to lose weight in the UK, prescription medications are now available for eligible adults through NHS specialist services or private prescribers. Understanding your options — including which weight loss injections you might qualify for — is the first step toward creating a realistic, sustainable plan tailored to your health needs.
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 Weight Loss Medications — What's Available
Three prescription-only weight management injections are currently licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All work by activating natural hormone pathways that help reduce appetite and support feeling fuller after smaller meals.
- Mounjaro: Once-weekly GIP and GLP-1 agonist; doses from 2.5 mg to 15 mg. Clinical trials showed average weight loss of 15–21% of body weight alongside diet and exercise.
- Wegovy: Once-weekly GLP-1 agonist; doses from 0.25 mg to 2.4 mg. Average weight loss approximately 15% of body weight in trials.
- Saxenda: Daily GLP-1 injection; doses from 0.6 mg to 3 mg. Slower titration than weekly injections.
Eligibility typically requires a BMI of 30 or above, or BMI of 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. However, you must have a clinical assessment before any medication is prescribed — a GP or licensed prescriber will evaluate your individual health needs first.
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 — How to Access Weight Loss Support
In the UK, you can access prescription weight loss medication through two routes. NHS access is via specialist tier 3 weight management services — you'll typically need a GP referral, and availability varies significantly by region (ICB) with waiting lists sometimes lasting months or longer. Private access is available through GPhC-registered online prescribers following a remote clinical assessment — this route is faster but involves a cost, usually £129–£320 per month depending on dose.
Whichever route you choose, effective weight loss involves combining medication with a reduced-calorie diet and increased physical activity. Start by calculating your BMI using our free BMI calculator above to understand your starting point, then have a conversation with your GP about whether prescription weight management might be appropriate for you. You can also use our GLP-1 weight loss calculator to explore potential outcomes if you become eligible for medication.
- 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 is the difference between Mounjaro, Wegovy, and Saxenda?
All three are prescription weight loss injections licensed in the UK, but they work slightly differently. Mounjaro activates two hormone pathways (GIP and GLP-1), while Wegovy and Saxenda activate one (GLP-1 only). Mounjaro and Wegovy are once-weekly injections; Saxenda is a daily injection. Clinical trials showed similar average weight loss of 14–21%, though individual results vary significantly.
Am I eligible for prescription weight loss medication on the NHS?
NHS eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. However, a GP assessment is always needed first. Some regions have longer waiting lists than others. Your GP can assess whether you qualify for NHS specialist services.
Can I get prescription weight loss medication privately without NHS referral?
Yes. Private UK prescribers offer online consultations followed by prescription if clinically appropriate. This route does not require NHS referral but involves a cost. The prescriber will still conduct a full health assessment to ensure the medication is safe for you individually.
How much weight can I expect to lose with prescription medication?
Clinical trials showed average weight loss of 14–21% of body weight over 12–18 months, alongside reduced-calorie diet and exercise. However, individual results vary significantly — some people lose more, some less. Weight loss medication works best combined with lifestyle changes, not as a replacement for them.
Do I need to use a weight loss planner with prescription medication?
Yes. A structured plan combining medication with dietary changes and physical activity gives the best results. Your GP or prescriber will help you plan this. You can also track progress using our free progress tracker on this site to monitor weight loss, energy levels, and other health markers over time.
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.