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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Vegan Weight Loss Program: Prescription Medication Options in the UK
A vegan weight loss program can be an effective lifestyle approach, but many people following plant-based diets benefit from additional support. If you're struggling to lose weight despite dietary changes, prescription weight loss medications are available in the UK through NHS weight management services and private prescribing. This guide explores medication options, eligibility criteria, and how to access prescription weight loss support alongside your vegan diet. Always consult your GP before starting any new weight loss programme.
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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 Medications
Three prescription-only medicines are licensed for weight management in the UK and can support your weight loss goals alongside dietary changes:
- Mounjaro (tirzepatide) — once-weekly injection, dual GIP and GLP-1 action, clinical trials showed average weight loss of 15–21% of body weight
- Wegovy (semaglutide) — once-weekly injection, GLP-1 medication, average weight loss approximately 15% in clinical trials
- Saxenda (liraglutide) — once-daily injection, GLP-1 medication, lower average weight loss but suitable for some patients
All three are prescription-only and require a clinical assessment to confirm eligibility. Use our GLP-1 weight loss calculator to estimate potential results at different doses. You're eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply (from 27.5).
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 Prescription Weight Loss Treatment in the UK
NHS access: Request a referral from your GP to a specialist weight management service (tier 3). These services provide comprehensive support including dietitian advice, which is particularly valuable for vegan dieters ensuring adequate nutrition. However, NHS waiting lists vary significantly by region and can be lengthy in some areas.
Private access: Licensed prescribers offer online consultations and prescriptions without NHS referral. This route is typically faster but involves private costs. Calculate your current BMI and health context using our free BMI calculator to prepare for any consultation. Whichever route you choose, prescription medication works best alongside your vegan diet, physical activity, and behaviour changes — not instead of them. Your GP can advise which option suits your circumstances.
- 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 I take prescription weight loss medication while following a vegan diet?
Yes. Mounjaro, Wegovy, and Saxenda work alongside any diet, including vegan diets. In fact, these medications can help reduce cravings and portion sizes, making it easier to stick to plant-based eating. Work with a vegan-aware dietitian to ensure adequate protein and micronutrient intake while using these medications.
How quickly will I lose weight on prescription medication?
Individual results vary significantly. Clinical trials showed average weight loss of 15–21% over 68–72 weeks with higher doses of Mounjaro, and approximately 15% with Wegovy. Weight loss typically becomes noticeable after 4–8 weeks, with continued loss over months. Use our weight loss calculator to estimate potential outcomes based on your current weight and the medication dose.
What is the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro uses dual GIP and GLP-1 action and typically produces slightly higher average weight loss (15–21%) compared to Wegovy's GLP-1 action alone (approximately 15%). Both require prescription and clinical assessment. Your prescriber will recommend the most suitable option based on your health profile.
Do I need to stop being vegan to use weight loss medication?
No. Prescription weight loss medications are not specific to any diet type. You can continue your vegan diet while using Mounjaro, Wegovy, or Saxenda. However, these medications can reduce appetite significantly, so ensure you're still meeting your nutritional needs through plant-based whole foods, fortified products, and possibly supplementation (B12, iron, omega-3s).
How do I know if I'm eligible for prescription weight loss medication on the NHS?
You're eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions (diabetes, high blood pressure, heart disease, sleep apnoea). Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Check your BMI using our free calculator above, then discuss eligibility with your GP.
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.