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
Free tracker included with every download this week
Weight Loss Plans Using UK Prescription Medication
If you're looking for effective weight management in the UK, prescription medication may be an option alongside diet and exercise. Several medications are now licensed for weight loss in the UK, with strong clinical evidence. This guide explains how prescription weight loss plans work, who is eligible, and how to access them through the NHS or privately. We'll also help you understand your personal BMI and weight management needs using our free tools.
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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 Medication
Three prescription medications are currently licensed for weight management in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, while Saxenda is a daily injection. All work by activating natural hormone pathways that help regulate appetite and support feeling fuller after meals.
- Mounjaro — dual GIP and GLP-1 agonist; clinical trials showed average weight loss of 15–21% body weight
- Wegovy — GLP-1 agonist; clinical trials showed average weight loss around 15% body weight
- Saxenda — GLP-1 agonist; established option with evidence for sustainable weight loss
Eligibility typically requires a BMI of 30 or above, or 27 and above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Results vary by individual and are most effective alongside a reduced-calorie diet and increased physical activity. Use our free BMI calculator above to check where you stand, and our weight loss calculator to estimate potential outcomes with GLP-1 medication.
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 Routes
NHS access: NICE has approved tirzepatide and semaglutide for use within NHS specialist weight management services. You'll typically need a referral from your GP to tier 3 specialist services, though availability varies by region and waiting times can be lengthy. Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber — no NHS referral needed. Costs range from approximately £129–£320 per month depending on medication and dose.
Start by speaking with your GP about your weight loss goals. They can assess whether prescription medication is suitable for you, discuss your BMI and health risks, and advise on NHS referral or private options. Many people use our progress tracker alongside medication to monitor their journey over weeks and months.
Q1: What is the eligibility criteria for prescription weight loss medication in the UK? A1: Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, may be eligible. These conditions include type 2 diabetes, prediabetes, high blood pressure, sleep apnoea, or cardiovascular disease. Lower BMI thresholds apply for South Asian, Black African, and Caribbean adults (BMI 27.5+). Always discuss eligibility with your GP or a prescriber. Q2: How much weight can you lose with prescription weight loss medication? A2: Clinical trials showed Mounjaro users lost an average of 15–21% body weight, and Wegovy users around 15% body weight, alongside diet and exercise. Individual results vary significantly based on adherence, lifestyle changes, and personal metabolism. Weight loss typically occurs gradually over 16 weeks and beyond. Q3: Can you get weight loss medication through the NHS in the UK? A3: Yes. NICE has approved tirzepatide (Mounjaro) and semaglutide (Wegovy) for NHS use within specialist tier 3 weight management services. Access requires a GP referral and availability varies by region. Private access is also available through online prescribers without NHS referral. Q4: What is the difference between Mounjaro and Wegovy? A4: Mounjaro is a dual GIP and GLP-1 agonist with a maximum dose of 15 mg weekly. Wegovy is a GLP-1 agonist with a maximum dose of 2.4 mg weekly. Clinical trial data suggests Mounjaro may produce slightly higher average weight loss, but both are effective. Choice depends on individual suitability and prescriber guidance. Q5: Is prescription weight loss medication safe for long-term use? A5: These medications have good safety data from clinical trials lasting up to 68 weeks. Common side effects include nausea and digestive changes, which typically improve over time. Serious side effects are rare but can include pancreatitis. Always report any concerns to your prescriber and have regular monitoring.- 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.
What is BMI and how is it calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in metres squared. It's the standard screening tool used by the NHS to assess whether adults are a healthy weight.
Is BMI accurate for everyone?
BMI is a useful screening tool but doesn't account for muscle mass, bone density, or body fat distribution. Athletes may have a high BMI without excess fat. The NHS recommends using BMI alongside waist circumference for a more complete picture.
What are GLP-1 medications like Mounjaro and Wegovy?
GLP-1 receptor agonists are prescription medications that mimic gut hormones to reduce appetite and help with weight loss. Mounjaro (tirzepatide) and Wegovy (semaglutide) are the two most widely used for weight management in the UK.
Am I eligible for GLP-1 weight loss medication in the UK?
Generally, you need a BMI of 30+ (obese) or 27+ with a weight-related health condition. You must be 18 or over. Use our BMI calculator to check.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with up to 22.5% weight loss. Wegovy (semaglutide) is GLP-1-only with up to 15-17% weight loss. Both are weekly injections.
Is this website free to use?
Yes, 100% free. No sign-up required. All tools work instantly in your browser and no personal data is stored on our servers.
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.