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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Diet Drinks for Weight Loss — Prescription Medication Options in the UK
Diet drinks are low-calorie alternatives to sugary beverages, but evidence shows they have limited impact on weight management when used alone. If you're looking for effective weight loss support in the UK, prescription medications like Mounjaro and Wegovy have demonstrated clinical evidence for helping eligible adults lose weight alongside lifestyle changes. This guide explains the prescription weight management options available through the NHS and privately, how to find out if you qualify, and why speaking to your GP is the first step.
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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
Several prescription weight loss medications are now licensed in the UK for adults struggling with their weight. These include Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist, and Wegovy (semaglutide), a GLP-1 receptor agonist. Both are given as once-weekly injections and are prescribed as part of a comprehensive weight management approach alongside diet and physical activity.
- Mounjaro: Clinical trials showed participants lost an average of 15–21% of body weight over 72 weeks at maximum dose, though individual results vary.
- Wegovy: Evidence from clinical trials indicated average weight loss of approximately 15% of body weight, again with results varying by individual.
- Saxenda (liraglutide): A daily GLP-1 injection also licensed for weight management in the UK.
These medications require a prescription and are suitable only for adults meeting specific eligibility criteria. Try our free GLP-1 weight loss calculator to understand potential weight loss projections 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.
Eligibility and How to Access Weight Loss Medication
In the UK, prescription weight loss medication is typically available to adults with a BMI of 30 or above, or BMI of 27–29 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds due to higher health risks at these levels.
Access is available through two routes: the NHS specialist weight management services (accessed via GP referral, though waiting lists vary by region), or private prescription services following an online clinical assessment with a UK-licensed prescriber. Check your BMI using our free BMI calculator to see where you fall on the healthy weight scale, then speak to your GP about your options.
- 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.
Do diet drinks help with weight loss?
Diet drinks are calorie-free but provide no nutritional benefit and don't address appetite regulation. Evidence suggests they have minimal impact on sustainable weight loss compared to water. They may help reduce calorie intake temporarily, but lifestyle changes and, where appropriate, prescription medication offer more reliable results for weight management in the UK.
What's the difference between Mounjaro and Wegovy?
Both are GLP-1-based injectable medications for weight loss, but Mounjaro is a dual GIP and GLP-1 agonist while Wegovy is GLP-1 only. Mounjaro starts at 2.5 mg and goes up to 15 mg weekly. Wegovy starts at 0.25 mg and reaches 2.4 mg weekly. Clinical trials showed slightly higher average weight loss with Mounjaro, though individual results vary significantly.
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 or above, or 27–29 with weight-related health conditions like diabetes or high blood pressure. Your GP or a licensed prescriber can assess your eligibility following a clinical consultation. Use our free BMI calculator to check your starting point, then discuss options with your healthcare provider.
Can I get weight loss injections on the NHS?
Yes, but access is through specialist tier 3 weight management services. You'll need a GP referral, and availability varies significantly by region. Some areas have long waiting lists. Alternatively, you can access prescription weight loss medication privately through GPhC-registered online prescribing services following a clinical assessment.
How much weight can I expect to lose with prescription medication?
Clinical trials showed average weight loss of 15–21% of body weight with Mounjaro and around 15% with Wegovy over several months, but individual results vary considerably. Weight loss depends on your starting weight, dose, adherence, diet, and physical activity. Always use conditional language — no outcome is assured for any individual.
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.