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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Smoothies for Weight Loss — Plus UK Prescription Options
While healthy smoothies can support weight loss as part of a balanced diet, many people in the UK find that prescription weight management medication alongside lifestyle changes delivers more significant results. If you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions, you may be eligible for GLP-1 weight loss injections like Mounjaro or Wegovy. This guide explores both dietary approaches and the prescription weight loss options available through the NHS and private prescribers in the UK.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Options — Mounjaro, Wegovy, and Eligibility
For eligible adults in the UK, prescription weight loss medications offer a medical approach to weight management that works alongside diet and exercise. The two most widely used are:
- Mounjaro (tirzepatide) — a once-weekly injection that activates GIP and GLP-1 pathways. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection with average weight loss of around 15% of body weight in clinical trials.
Both are prescription-only medicines requiring clinical assessment. Eligibility includes adults with a BMI of 30 kg/m² or above, or BMI 27–29.9 with weight-related conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may have lower BMI thresholds due to higher health risks. Individual results vary significantly. Use our free GLP-1 weight loss calculator above to explore potential outcomes 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.
Getting Started — NHS vs Private Routes in the UK
Access to prescription weight loss medication in the UK varies by route. Through the NHS, you can ask your GP for referral to a tier 3 specialist weight management service, though waiting lists and availability differ by region. Alternatively, private prescribing through registered online clinics is quicker — a licensed prescriber reviews your health and issues a prescription if appropriate. Both routes require a clinical assessment to ensure the medication is safe for you. Your GP remains your best first point of contact to discuss whether prescription weight loss support is suitable for your personal situation and health history.
- 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 smoothies alone help me lose weight?
Smoothies can support weight loss if they're lower in calories and sugar and form part of a calorie-deficit diet. However, they work best alongside physical activity and balanced meals. For more significant weight loss, many people benefit from additional support — discuss options with your GP.
What ingredients should I put in a weight loss smoothie?
Focus on protein (Greek yoghurt, protein powder), fibre (berries, oats, spinach), and healthy fats (nut butter, seeds). Limit added sugars and fruit juice. Measure portions carefully as smoothies can be high-calorie despite appearing healthy.
Am I 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 weight-related conditions like diabetes or high blood pressure. Use our free BMI calculator to check your current BMI, then speak with your GP about whether prescription support is appropriate for you.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1). Clinical trials suggest Mounjaro may produce slightly larger average weight loss, though individual results vary. Your prescriber will recommend the most suitable option for your health profile.
How quickly will I lose weight on prescription medication?
Clinical trials show weight loss typically begins within 2–4 weeks and continues over 72 weeks. Average results are 15–21% of body weight depending on the medication and dose. However, results vary significantly between individuals. Track your progress using our free progress tracker to monitor your personal journey.
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.