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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Cabbage Soup Diet and Weight Loss Medication in the UK
The cabbage soup diet is a low-calorie diet plan popular in the UK, but research shows it's not sustainable for long-term weight loss on its own. If you're looking for effective weight management alongside dietary changes, several prescription weight loss options are now available in the UK. Understanding your eligibility for medications like Mounjaro, Wegovy, or Saxenda — and how they compare to fad diets — can help you make an informed choice about your weight loss journey. This guide explains UK-licensed options and how to start a conversation with your GP.
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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 medications are currently licensed in the UK for weight management in eligible adults:
- Mounjaro (tirzepatide) — A once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight, though individual results vary. Maximum dose is 15 mg weekly.
- Wegovy (semaglutide) — A once-weekly GLP-1 injection. In clinical trials, participants lost approximately 15% of body weight on average. Maximum dose is 2.4 mg weekly.
- Saxenda (liraglutide) — A daily GLP-1 injection. Less commonly prescribed than Mounjaro or Wegovy but still available.
Unlike crash diets, these medications work alongside a reduced-calorie diet and increased physical activity. All three are prescription-only and require a clinical assessment to determine suitability. You can check your BMI using our free BMI calculator above to understand where you sit on NHS weight categories before speaking to your GP.
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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 Access and Private Options in the UK
Access to prescription weight loss medication varies across the UK. The NHS route involves referral to a tier 3 specialist weight management service through your GP. Waiting times can be lengthy in some areas, but services are free. Private access is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber — this route is faster but involves costs.
To find out if you're eligible, calculate your BMI and discuss it with your GP. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Track your weight loss journey using our free progress tracker once you've started any treatment plan.
- 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.
Is the cabbage soup diet effective for long-term weight loss?
The cabbage soup diet can produce short-term weight loss due to its very low calorie content, but research shows most people regain weight after stopping. It lacks nutritional balance and isn't sustainable. For lasting weight management, combining lifestyle changes with NHS weight loss support or prescription medication is more effective.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions, may be eligible. Conditions include type 2 diabetes, prediabetes, high blood pressure, abnormal cholesterol, or cardiovascular disease. Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Your GP can assess your individual eligibility.
Can I use prescription weight loss medication without changing my diet?
No. Mounjaro, Wegovy, and Saxenda are prescribed alongside a reduced-calorie diet and increased physical activity. These medications support but don't replace lifestyle changes. The most effective weight loss combines medication, diet, and exercise — not medication alone.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro is a dual GIP and GLP-1 agonist; Wegovy is a GLP-1 agonist only. Clinical trials showed Mounjaro produced slightly higher average weight loss (15–21% vs approximately 15%), though results vary individually. Both are once-weekly injections. Your prescriber will recommend based on your health profile and suitability.
How quickly can I access prescription weight loss medication on the NHS?
NHS access depends on your region and tier 3 service availability. Waiting times vary from weeks to months or longer in some areas. Private access is typically faster — usually within days after clinical assessment. Ask your GP about NHS waiting times in your area, or explore private options if you prefer immediate access.
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.