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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gradual weight management Diet — UK Prescription Medication Options
If you're looking to lose weight quickly, prescription medications may be an option alongside dietary changes. In the UK, three GLP-1 and GIP receptor agonist medications are licensed for weight management: Mounjaro, Wegovy, and Saxenda. These work by helping regulate appetite and food cravings. However, they're only available on prescription after a clinical assessment. This guide explains your options, eligibility criteria, and how to access weight loss medication through the NHS or privately.
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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-Licensed Prescription Weight Loss Medications
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, injected once weekly. Clinical trials showed average weight loss of around 15–21% of body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, injected once weekly. Evidence from clinical trials demonstrated average weight loss of approximately 14.9% of body weight at 68 weeks.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, injected daily. Average weight loss is typically lower than Mounjaro or Wegovy, but it remains a licensed option.
All three medications work by helping to reduce appetite, increase feelings of fullness, and support weight management when combined with lifestyle changes. Individual results vary significantly. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses.
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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.
Eligibility and How to Access Weight Loss Medication in the UK
You may be eligible for prescription weight loss medication in the UK if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or heart disease). Lower BMI thresholds may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage due to increased health risk at lower weights.
Weight management medication is available through the NHS (via specialist tier 3 services, though waiting times vary by region) or privately (through online consultations with UK-licensed prescribers). Your GP can discuss whether prescription weight loss medication is appropriate for you, or you can seek a private clinical assessment. Check your BMI using our free BMI calculator to understand where you stand.
- 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 I get gradual weight management medication on the NHS in the UK?
Yes, but access varies by region. Mounjaro and Wegovy are approved by NICE for NHS specialist weight management services (tier 3). However, waiting times can be lengthy in many areas. Your GP can refer you to your local specialist service, or you can explore private prescribing options if you meet eligibility criteria.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro uses a dual GIP and GLP-1 mechanism and showed slightly higher average weight loss (~20.9% at maximum dose) in trials. Wegovy is a GLP-1-only medication with average weight loss around 14.9%. Both work best alongside dietary changes and exercise. Results vary between individuals.
How quickly will I lose weight on prescription weight loss medication?
The NHS recommends losing 0.5–1 kg per week for sustainable results. Prescription medications like Mounjaro and Wegovy support this when combined with a reduced-calorie diet. Clinical trials show ongoing weight loss over weeks and months, not rapid overnight change. Your prescriber will monitor your progress.
Am I eligible for weight loss medication?
You may be eligible if your BMI is 30 or above, or 27–29 with weight-related health conditions like diabetes or high blood pressure. Use our free BMI calculator to check your BMI, then discuss options with your GP or a private prescriber who can assess your individual health situation.
What's the cost of private weight loss medication in the UK?
Private prescription weight loss medication typically costs £129–£320 per month depending on the drug, dose, and provider. This is not usually available on the NHS for standard GP prescription, though NHS specialist services may offer it. Private clinics handle assessment, prescription, and dispensing directly.
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.