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 Weight Loss Diets in the UK
Finding the best weight loss diet depends on your individual health, lifestyle, and goals. While sustainable dietary changes form the foundation of weight management in the UK, prescription medications are also available for eligible adults. This guide covers evidence-based diet approaches, how prescription weight loss medication works alongside dietary changes, and how to find out if you qualify for NHS or private treatment. Whether you're exploring dietary options alone or considering medication support, understanding what's available helps you make informed choices 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 Weight Loss Medications and Diet Support
For adults meeting NHS eligibility criteria, prescription weight loss medications can be combined with dietary changes for more significant results. Three medications are licensed in the UK:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 pathways. Clinical trials showed an average weight loss of 15–21% body weight alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Average weight loss in trials was approximately 15% body weight over 68 weeks with lifestyle support.
- Saxenda (liraglutide) — a daily GLP-1 injection, available as an older option with similar evidence base.
All three are prescription-only and require a clinical assessment before being prescribed. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses. Individual results vary significantly — medication works best when combined with weight management UK support through diet and movement.
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 Getting Started
NHS weight loss medication access: Typically through specialist tier 3 weight management services. You'll need a referral from your GP, and availability varies by region (ICB). Waiting lists can be lengthy in many areas.
Private access: Available through online prescribing services following a clinical assessment, without NHS referral.
Start by speaking with your GP about your weight loss goals. They can assess your BMI, health conditions, and eligibility. You can use our free BMI calculator to check your starting point before your appointment. Your GP can discuss whether prescription weight loss is appropriate alongside dietary support, or recommend NHS tier 2 programmes (behavioural support, group classes) first.
Evidence-based diet approaches include the Mediterranean diet (strong cardiovascular benefits), low-calorie structured plans (500 kcal deficit = ~0.5 kg/week loss), intermittent fasting, and low-carbohydrate eating. NHS guidance recommends losing no more than 0.5–1 kg per week for sustainable results. Even a 5–10% reduction in body weight improves blood pressure, blood sugar, and mobility.
For weight management UK success: combine dietary changes with movement, sleep, and stress management. Track progress using our free progress tracker alongside diet and any medication. The best diet is one you can sustain long-term alongside a supportive GP relationship.
- 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 best weight loss diet for me?
The best diet depends on your lifestyle, preferences, and health conditions. Mediterranean, intermittent fasting, and structured low-calorie approaches all have evidence. Your GP can discuss options, and lifestyle changes form the foundation. If eligible, prescription medication can enhance results when combined with dietary support.
Can I get weight loss medication on the NHS in the UK?
Yes, if you meet eligibility criteria (BMI ≥30, or ≥27 with weight-related health conditions). Access is through specialist tier 3 weight management services via GP referral. Availability and waiting times vary significantly by region. Discuss options with your GP.
How much weight can Mounjaro or Wegovy help me lose?
Clinical trials showed average weight loss of 15–21% body weight with Mounjaro and approximately 15% with Wegovy, combined with diet and exercise. Individual results vary — some lose more, some less. These are averages, not assures. Your prescriber can discuss realistic expectations.
What is the difference between Mounjaro and Wegovy?
Both are once-weekly injections. Mounjaro (tirzepatide) activates dual GIP+GLP-1 pathways; Wegovy (semaglutide) activates GLP-1 only. Mounjaro showed slightly higher average weight loss in trials. Both require prescription and clinical assessment. Your prescriber can advise which suits you.
How quickly can I lose weight with diet alone?
NHS guidance suggests 0.5–1 kg per week with a sustainable calorie deficit (approximately 500 kcal/day). This is safe, sustainable, and reduces muscle loss. Faster loss is possible with medical support but requires supervision. Track your progress with our free progress tracker to monitor results.
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.