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 Shake and Prescription Medication in the UK
Weight loss shakes can support a reduced-calorie diet, but for significant weight management in the UK, prescription medications are available for eligible adults. If you're considering weight loss options, prescription medications like Mounjaro and Wegovy have strong clinical evidence and are available through both NHS specialist services and private prescribing. Understanding what's available through the NHS weight loss pathway, alongside lifestyle changes, can help you find the right approach for your health goals.
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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 Options
For eligible UK adults, three prescription-only weight management medications are available: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 and GIP/GLP-1 receptor agonists that work alongside lifestyle changes to support weight management.
Eligibility: Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnoea) may qualify. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply due to increased health risks at lower weights.
Clinical evidence: In trials, Mounjaro helped participants lose an average of 15–21% of body weight, while Wegovy supported approximately clinically studied weight loss — though individual results vary significantly. These medications work best alongside a reduced-calorie diet and increased physical activity.
Use our free GLP-1 weight loss calculator above to explore potential outcomes at different doses, and our BMI calculator to check your starting point.
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 Weight Loss Medication: NHS vs Private Route
NHS access: Referral to a tier 3 specialist weight management service from your GP is the first step. NICE has approved tirzepatide (Mounjaro) for use within NHS specialist services, though availability and waiting times vary significantly by region.
Private route: GPhC-registered online pharmacies offer prescription weight loss medication following an online clinical assessment with a UK-licensed prescriber. This route doesn't require NHS referral but involves private costs.
Next steps: Start by speaking with your GP about whether prescription weight loss treatment might be suitable for you. They can assess your individual health, discuss your options, and refer you to specialist services if appropriate. Even if NHS wait times are long, knowing your eligibility and understanding the options available can help you make informed decisions about weight management in the UK.
- 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 a weight loss shake better than prescription medication?
Weight loss shakes can support a calorie-controlled diet as part of a healthy eating plan. However, prescription medications like Mounjaro and Wegovy have clinical trial evidence showing they can help with significant weight loss when combined with lifestyle changes. The best approach depends on your individual health, BMI, and any weight-related conditions. Your GP can help you decide which option is right for you.
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 27–29.9 with at least one weight-related health condition (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 may apply. A prescriber will assess your individual eligibility.
Can I get Mounjaro or Wegovy on the NHS in the UK?
Yes, Mounjaro (tirzepatide) is approved for use within NHS specialist weight management services following a GP referral. Availability varies by region, and waiting lists can be long in some areas. Alternatively, prescription weight loss medication is available privately through online prescribing services following a clinical assessment.
What's the difference between a weight loss shake and a weight loss injection?
Weight loss shakes are meal replacements or supplements providing controlled calories. Weight loss injections (like Mounjaro and Wegovy) are prescription medications that work by activating hormone pathways to reduce appetite and support feeling fuller. Injections have clinical trial evidence for significant weight loss when used alongside diet and exercise, whereas shakes work primarily through calorie reduction.
How do I start the weight loss medication process in the UK?
Begin by speaking with your GP about your weight management goals and health. They can assess whether prescription medication might be appropriate, discuss any health concerns, and refer you to a specialist weight management service if eligible. You can also check your BMI using our free BMI calculator to understand your starting point before your appointment.
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.