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
Best Tips For Weight Loss in the UK
Losing weight successfully requires a combination of dietary changes, physical activity, and in some cases, prescription support. If you're struggling with weight management in the UK, understanding your options — from lifestyle adjustments to prescription weight loss medication — can help you find an approach that works for you. This guide covers practical strategies and explores UK-licensed prescription options available to eligible adults, including how to discuss your options with your GP.
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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 Loss Options
For adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, prescription weight loss medication may be an option. Three medications are licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 pathways. Clinical trials showed participants lost an average of 15–21% body weight alongside diet and exercise changes.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Evidence suggests average weight loss of around 15% body weight over 68 weeks in clinical trials.
- Saxenda (liraglutide) — a daily GLP-1 injection, an alternative option for eligible adults.
All are prescription-only and require a clinical assessment. Weight loss medications work best combined with reduced-calorie diet and increased physical activity. Individual results vary significantly. Our GLP-1 weight loss calculator can help you explore projected outcomes at different doses if you're considering this route.
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 and Next Steps
In the UK, weight loss medication access is available through two routes. NHS specialist tier 3 weight management services can prescribe these medications following referral from your GP, though waiting lists vary by region and availability is limited. Private access is available through GPhC-registered online pharmacies following an online clinical assessment — no NHS referral needed, though costs typically range from £129–£320 monthly depending on dose.
Start by speaking with your GP about your weight loss goals. They can assess your individual health, discuss whether prescription medication might be suitable, refer you to NHS specialist services if appropriate, or advise on private options. Use our BMI calculator to understand your starting point, and our progress tracker to monitor changes once you begin any weight loss programme.
- 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's the safest rate of weight loss?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week for sustainable, healthy results. This typically requires a calorie deficit of around 500 kcal per day. Faster weight loss is possible with medical support but carries higher risks of muscle loss and nutritional deficiencies.
Can I get weight loss medication on the NHS?
Yes, NHS specialist weight management services (tier 3) can prescribe medications like Mounjaro and Wegovy, but access requires GP referral and varies significantly by region. Waiting times can be lengthy. Private online prescribing offers faster access if you meet eligibility criteria and can cover costs privately.
Am I eligible for prescription weight loss medication?
Generally, you may be eligible if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Your GP or prescriber will assess individual eligibility.
How much weight can I expect to lose with GLP-1 medication?
Clinical trials show average weight loss of 15–21% body weight over 68 weeks, depending on the medication and dose. However, individual results vary significantly — some people lose more, some less. Results are achieved alongside reduced-calorie diet and increased physical activity, not medication alone.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) activates GLP-1 only. Mounjaro starts at 2.5 mg and goes up to 15 mg weekly; Wegovy starts at 0.25 mg up to 2.4 mg weekly. Clinical trial data suggests similar weight loss outcomes, but individual response varies. Your prescriber will advise which is appropriate 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.