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 Juices For Weight Loss โ And When To Consider Medication
While fresh juices can support a healthy diet, they're often high in natural sugars and calories โ so they work best as part of a calorie-controlled approach rather than a weight loss solution on their own. If you're looking for more substantial support with weight management in the UK, prescription medications are available for eligible adults. This guide covers both dietary approaches and the medical options your GP can discuss with you.
10,000+ calculations today ยท NHS-aligned thresholds ยท 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/mยฒ).
While BMI isn't a perfect measure โ it doesn't account for muscle mass, bone density, or fat distribution โ 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 โ 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.
Prescription Weight Loss Options Available in the UK
If diet and lifestyle changes alone haven't worked, prescription weight loss medications are now available through the NHS and private prescribers for eligible UK adults. The three main options are:
- Mounjaro (tirzepatide) โ a once-weekly injection that activates two natural hormone pathways to reduce appetite and support weight management. Clinical trials showed average weight loss of 15โ21% of body weight.
- Wegovy (semaglutide) โ a once-weekly GLP-1 injection. In clinical trials, participants lost an average of 14.9% of their body weight alongside a reduced-calorie diet.
- Saxenda (liraglutide) โ a daily GLP-1 injection, offering an alternative for those preferring daily dosing.
All three are prescription-only and require assessment by a licensed prescriber to confirm suitability for you personally.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care โ 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 โ 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 โ completely free.
NHS vs Private Access and How to Check Your Eligibility
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or BMI of 27 or above with a weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea). Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage.
NHS route: Ask your GP for a referral to a specialist weight management service. Private route: Online prescribing services offer assessment and prescriptions without NHS referral, though costs apply. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses, and use the BMI calculator to check where you stand against eligibility thresholds.
- 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 โ 5mg โ 7.5mg โ 10mg โ 12.5mg โ 15mg
- GLP-1 receptor agonist
- Up to 15โ17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg โ 0.5mg โ 1mg โ 1.7mg โ 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 | 15โ22.5% | 12โ17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20โ32 weeks | 16โ20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | ยฃ150โยฃ250/month | ยฃ150โยฃ300/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 โ 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 juices actually helpful for weight loss?
Fresh juices contain vitamins and nutrients, but they're often high in natural sugars and calories whilst lacking the fibre of whole fruit. A 250ml glass of orange juice contains around 110 calories and 26g of sugar. For weight loss, whole fruits, vegetables, and plenty of water are usually better choices. Use juices sparingly as part of a balanced diet.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), whilst Wegovy (semaglutide) activates one (GLP-1 only). Clinical trial results were comparable, but individual responses vary. Your prescriber will assess which is more suitable for you.
Can I get weight loss medication on the NHS?
Yes. Mounjaro and Wegovy are now approved by NICE for use within NHS specialist weight management services. However, access varies significantly by region and often involves waiting lists. Your GP can refer you to your local tier 3 weight management service to explore eligibility and availability.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15โ21% of body weight over several months. However, individual results vary significantly and depend on diet, activity level, and how your body responds. These medications work best alongside lifestyle changes, not as a replacement for them.
Do I need to follow a diet if I'm taking Mounjaro or Wegovy?
Yes. Prescription weight loss medications are most effective when combined with a reduced-calorie diet and increased physical activity. The medication supports appetite control, but you still need to make conscious food choices. Your GP or specialist will provide dietary guidance as part of your treatment plan.
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.