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 Shakes and Prescription Medication in the UK
Weight loss shakes can be a practical tool for reducing calories, but they work best alongside other approaches — including prescription medication for eligible adults. The UK has several NHS-approved weight management options available, from specialist services to private prescribing. This guide explains what's available, who qualifies, and how to find out if prescription weight loss medication might support your weight management journey alongside dietary changes and physical activity.
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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 Prescription Weight Loss Medication Options
Three prescription-only medicines are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These work by activating natural appetite-regulating hormones in the gut.
Mounjaro is a once-weekly injection using dual GIP and GLP-1 receptor action. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks alongside reduced-calorie diet and increased physical activity — results vary significantly between individuals.
Wegovy is a once-weekly GLP-1 injection. Clinical trials demonstrated average weight loss of approximately 15% over 68 weeks. Saxenda is a daily GLP-1 injection with similar efficacy. All three require a prescription and clinical assessment. Use our free GLP-1 weight loss calculator to explore projected outcomes at different dose levels.
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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.
NHS vs Private Access and How to Find Out if You're Eligible
NHS access: Available through tier 3 specialist weight management services following GP referral. Availability and waiting times vary significantly by region (ICB). Eligibility typically requires BMI ≥30, or BMI 27–29 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease.
Private access: Available through GPhC-registered online pharmacies following an online clinical assessment — no NHS referral needed. Costs vary by dose and provider (typically £129–£320 monthly).
First step: Speak to your GP about your weight management goals. They can assess your individual health, discuss whether prescription medication is suitable, and explain NHS options in your area. Our free BMI calculator can help you understand your current position.
- 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 weight loss shakes alone help me lose weight?
Weight loss shakes can reduce calorie intake if they replace higher-calorie meals, but sustainable weight loss requires a calorie deficit alongside increased physical activity. Shakes work best as part of a broader lifestyle approach — they are not a standalone solution. The NHS recommends losing 0.5–1 kg per week through combined dietary and activity changes.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or BMI 27–29 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, or sleep apnoea), may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds due to higher health risk. Your GP can assess your individual eligibility.
How much weight might I 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 68–72 weeks — alongside reduced-calorie diet and increased physical activity. Individual results vary considerably. Some people lose more, some less. A prescriber will discuss realistic outcomes based on your health and circumstances.
How do I access weight loss medication on the NHS?
Ask your GP for a referral to your local tier 3 specialist weight management service. They will assess you and discuss available treatment options — which may include prescription medication. Waiting times vary by region. Your GP can tell you typical timescales in your area. Private access is available immediately through online clinical assessment if you prefer.
Is weight management medication suitable if I use weight loss shakes?
Yes. Prescription weight loss medications are designed to work alongside dietary changes, including structured meal plans or nutritional products like shakes. They enhance appetite regulation but do not replace the need for a reduced-calorie diet and physical activity. Your prescriber will discuss a comprehensive approach tailored to your needs.
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.