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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Liquid Diet and Weight Loss in the UK
A liquid diet can be an effective short-term weight loss tool, but for many people in the UK, prescription weight management medication offers additional support. This guide explains how liquid diets work, who might benefit from them, and how prescription options like Mounjaro and Wegovy fit into a broader weight loss strategy. Whether you're considering dietary changes or exploring medication options, understanding what's available through the NHS and private healthcare can help you make an informed decision about your weight management journey.
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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 Prescription Weight Loss Options
If you're exploring weight management in the UK, prescription medications are available for eligible adults. Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1 and dual GIP/GLP-1 receptor agonists licensed for weight management, often used alongside dietary approaches like liquid diets. Saxenda (liraglutide) is also available as a daily injection option.
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply due to increased health risks at lower weights. Clinical trials showed that Mounjaro helped participants lose an average of 15–21% of their body weight, though individual results vary significantly. These medications work alongside dietary changes, including structured approaches like temporary liquid diets, to support sustainable weight loss.
Use our free GLP-1 weight loss calculator to estimate potential weight loss outcomes at different medication doses, and our BMI calculator to check your current BMI and eligibility bracket.
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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 vs. Private Access and Next Steps
NHS access to prescription weight loss medication is through specialist tier 3 weight management services, typically requiring a GP referral. Availability varies significantly by region, and waiting lists can be lengthy in many areas. Private access is available through online consultations with UK-licensed prescribers, without requiring an NHS referral, though costs apply (typically £150–£300 monthly depending on dose).
If you're considering prescription weight loss support alongside a liquid diet or other dietary approach, the first step is speaking with your GP. They can assess your individual health, discuss your weight loss goals, and explain local NHS options. You can also explore private prescribing through GPhC-registered online services if you prefer faster access. Either route involves a clinical assessment to ensure the medication is appropriate for your health profile. Remember that weight management is most effective when combining medication, dietary changes, and increased 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.
Will a liquid diet alone help me lose weight long-term?
Liquid diets can support short-term weight loss by creating a calorie deficit, but research suggests they work best as part of a broader lifestyle approach. The NHS recommends sustainable weight loss of 0.5–1 kg per week. For longer-term results, combining dietary changes with increased physical activity and, if eligible, prescription medication can be more effective. Your GP can advise on the best approach for your individual circumstances.
Who is eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, eligibility may begin at a BMI of 27.5 or above. A GP or prescriber will assess your individual health to confirm eligibility.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy over several months. However, individual results vary significantly based on dose, lifestyle changes, and personal metabolism. Results are achieved alongside a reduced-calorie diet and increased physical activity — medication alone is not sufficient.
Can I use a liquid diet while taking weight loss medication?
Combining a temporary liquid diet with prescription medication should only be done under medical supervision. Your prescriber can advise whether this is appropriate for your health profile, as very low-calorie diets require monitoring. Always inform your prescriber of any significant dietary changes you plan to make.
How do I access weight loss medication through the NHS?
Ask your GP for a referral to your local tier 3 specialist weight management service. They will assess your eligibility and discuss treatment options, which may include prescription medication. Waiting times vary by region. Alternatively, private online prescribing services offer faster access if you meet eligibility criteria, though costs apply.
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.