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
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Easy Weight Loss Diet — UK Prescription Weight Management Options
Looking for an easy weight loss diet approach? While lifestyle changes remain the foundation of sustainable weight management in the UK, prescription medications can provide significant support for eligible adults. This guide covers NHS-approved weight loss injections, how they work alongside dietary changes, and whether you might be eligible for prescription support through either NHS or private routes. We'll help you understand your options and how to take the first step towards your goals.
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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 — What's Available
Three prescription-only medications are licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These work as GLP-1 (and GIP/GLP-1) receptor agonists, helping reduce appetite, support feeling fuller after meals, and slow gastric emptying. Clinical trials show these can support meaningful weight loss when combined with reduced-calorie diet and increased physical activity.
- Mounjaro: Once-weekly injection, doses from 2.5 mg to 15 mg. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks.
- Wegovy: Once-weekly injection, doses from 0.25 mg to 2.4 mg. Clinical trials showed average weight loss of approximately 15% of body weight.
- Saxenda: Daily injection, doses from 0.6 mg to 3 mg. Also licensed for weight management in UK adults.
All three require a prescription following clinical assessment. A prescriber will evaluate your BMI, health conditions, and suitability before treatment begins. Use our GLP-1 weight loss calculator above to explore potential outcomes at different doses — individual results vary significantly.
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 — How to Find Out If You're Eligible
The NHS offers weight loss medication through specialist tier 3 weight management services, though availability and waiting times vary significantly by region. Most people access treatment through private online prescribing after a clinical assessment with a UK-licensed prescriber.
NHS route: Ask your GP for a referral to your local specialist weight management service. Be prepared for waiting lists, which can extend several months in some areas.
Private route: Prescription weight loss medication is available through GPhC-registered online pharmacies following a straightforward clinical assessment. This typically takes days rather than months.
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Calculate your BMI now using our free BMI calculator to understand where you stand, then speak with a healthcare professional about whether prescription medication is right for you.
- 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.
Can prescription weight loss medication replace diet and exercise?
No. UK-licensed weight loss medications work best alongside a reduced-calorie diet and increased physical activity. These drugs support your efforts — they're not a standalone solution. Think of them as a helpful tool alongside your lifestyle changes, not instead of them.
How much weight can I expect to lose?
Clinical trials show average weight loss of 15–21% of body weight, but individual results vary significantly. Some people lose more, some less. Factors including diet adherence, exercise, metabolism, and dose all influence outcomes. Your prescriber will discuss realistic expectations during assessment.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1). Both are once-weekly injections. Clinical trials suggest Mounjaro may offer slightly greater average weight loss, though both are effective. Your prescriber will help determine which suits you best.
How quickly can I get started with weight loss medication?
NHS access involves referral and waiting lists — timeline varies by region, sometimes months. Private access is faster — typically days to weeks from online consultation to receiving your prescription. Both routes require clinical assessment to ensure the medication is safe and appropriate for you.
Are weight loss injections safe long-term?
These medications have been used safely in clinical practice for years. However, they're prescription-only for a reason — they're not suitable for everyone. Common side effects include nausea and digestive changes, which often improve over time. Your prescriber will monitor you throughout treatment and discuss any concerns.
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.