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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Weight Loss Diet Plans — UK Medication Options
When it comes to weight management in the UK, diet plans work best when tailored to your individual needs. While lifestyle changes remain the foundation of sustainable weight loss, prescription weight loss medication is now available to eligible adults through both NHS and private routes. Understanding your options — including medication combined with diet and exercise — empowers you to make informed decisions about your health. This guide covers UK-licensed weight loss medication, eligibility criteria, and how to access support.
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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
Three prescription-only weight loss medications are licensed in the UK for adults with obesity or overweight with related health conditions:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, once-weekly injection. In clinical trials, participants lost an average of 15–21% body weight over 72 weeks alongside diet and exercise.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, once-weekly injection. Clinical trials showed average weight loss of approximately 15% body weight at the maximum dose.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, once-daily injection. Average weight loss approximately 5–8% body weight.
Eligibility typically requires a BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Lower thresholds may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Individual results vary significantly, and medications work best combined with dietary changes and increased physical activity. Use our free GLP-1 weight loss calculator to estimate potential weight loss outcomes at different doses.
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.
Accessing Weight Loss Support in the UK
NHS route: Ask your GP about referral to your local tier 3 specialist weight management service. Availability and waiting times vary significantly by region (ICB). Some areas offer NICE-approved tirzepatide through NHS specialist services, though waiting lists can be lengthy.
Private route: Prescription weight loss medication is available through GPhC-registered online prescribers following a clinical assessment. This allows faster access without NHS waiting lists, though costs range from approximately £129–£320 monthly depending on dose and provider.
Before starting any weight loss medication, discuss your medical history, current medications, and health goals with your prescriber or GP. Check your BMI using our free BMI calculator to help guide your conversation. Successful weight management combines medication (if eligible), calorie reduction of around 500 kcal daily for approximately 0.5 kg weekly loss, and regular physical activity.
- 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 and Wegovy for weight loss?
Both are once-weekly injections licensed for weight management in the UK. Mounjaro is a dual GIP/GLP-1 agonist with average weight loss of 15–21% in trials, whilst Wegovy is a GLP-1 agonist alone with average weight loss of about 15%. Mounjaro has a higher starting dose and longer escalation period. Individual results vary considerably, and your prescriber will assess which is more suitable based on your health profile.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, heart disease). Lower BMI thresholds apply if you're of South Asian, Chinese, or Black African heritage. Your GP or a licensed prescriber will assess your eligibility following a clinical evaluation of your health.
What's the difference between NHS and private weight loss medication in the UK?
NHS access is through specialist tier 3 weight management services (via GP referral), with regional variation and waiting lists. Private prescribing offers faster access through online clinical assessments with GPhC-registered pharmacies, typically costing £129–£320 monthly. Both require a prescription and clinical assessment; the main difference is access speed and cost.
How much weight can I expect to lose with prescription weight loss medication?
Average clinical trial results show 15–clinically studied weight loss with Mounjaro and approximately 15% with Wegovy over 12–18 months, alongside reduced-calorie diet and exercise. However, individual results vary significantly based on starting weight, adherence, diet, and activity level. Some people lose more, some less. Results are not assured; medication works best combined with sustained lifestyle changes.
Do weight loss injections work without diet and exercise changes?
No. Prescription weight loss medications are most effective when combined with a reduced-calorie diet and increased physical activity. These medications support appetite control and feelings of fullness, but weight loss ultimately requires a calorie deficit. The NHS recommends aiming for 0.5–1 kg weight loss per week through a combination of medication (if prescribed), diet changes, and exercise. Your progress tracker can help monitor your journey.
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.