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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Semaglutide Weight Loss Dosage Chart for UK Adults
Semaglutide is a prescription-only weekly weight loss injection licensed in the UK under the brand name Wegovy. Understanding the dosage schedule, measured in milligrams per dose, is essential before starting treatment. This guide explains the semaglutide weight loss dosage chart used in UK clinical practice, NHS eligibility criteria, and how the escalation schedule works. Individual prescribing varies based on clinical assessment by your GP or a licensed prescriber.
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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.
Semaglutide Dosage Schedule and NHS Context
Semaglutide for weight loss is administered as a once-weekly injection. The dosage escalates over 16+ weeks, starting at 0.25 mg and increasing to the maximum maintenance dose of 2.4 mg. Each dose is given as a subcutaneous injection, typically into the stomach, thigh, or upper arm.
- Weeks 1–4: 0.25 mg (starting dose)
- Weeks 5–8: 0.5 mg
- Weeks 9–12: 1 mg
- Weeks 13–16: 1.7 mg
- Week 17 onwards: 2.4 mg (maintenance)
In the STEP-1 clinical trial, adults taking semaglutide 2.4 mg alongside a reduced-calorie diet achieved an average weight loss of approximately 14.9% of body weight over 68 weeks. However, individual results vary significantly. Your prescriber will assess whether escalating to the full dose is appropriate for you based on tolerability and response.
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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
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NHS Access and Private Routes in the UK
In the UK, semaglutide weight loss medication (Wegovy) is accessible through two main routes. NHS prescribing is limited to specialist tier 3 weight management services—referral from your GP is required, and availability varies significantly by region. Waiting lists can be lengthy in many areas. Alternatively, private prescribing is available through GPhC-registered online pharmacies following an online clinical assessment, with no NHS referral needed. Adults with a BMI of 30 kg/m² or above, or 27 kg/m² with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease), may be eligible. Use our free GLP-1 weight loss calculator to project potential outcomes at different doses.
- 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 the difference between semaglutide for weight loss and Ozempic?
Both Wegovy and Ozempic contain semaglutide, but they are different medications. Ozempic is approved for type 2 diabetes at doses up to 2 mg and is not licensed for weight loss in the UK. Wegovy is the licensed weight management version, used at doses up to 2.4 mg. Using Ozempic for weight loss is off-label prescribing and not recommended.
How quickly does semaglutide weight loss work?
Weight loss typically begins within the first few weeks, but the most significant results appear between weeks 8 and 16 as you reach the full maintenance dose of 2.4 mg. The STEP trial showed average weight loss of 14.9% at 68 weeks. Results depend on diet, activity, and individual metabolism—always combine medication with lifestyle changes.
Can my GP prescribe semaglutide on the NHS?
Standard GP practices do not typically prescribe semaglutide for weight loss on the NHS. Access is through specialist tier 3 weight management services, which require a GP referral. Availability, waiting times, and eligibility vary by region. Contact your local NHS weight management service or speak to your GP about referral options.
What happens if I miss a semaglutide injection?
If you miss a dose by more than 4 days, skip that dose and take your next injection on the scheduled day. If you miss by fewer than 4 days, inject as soon as you remember. Never take a double dose. Maintain a gap of at least 3 days between injections. Speak to your prescriber if you frequently miss doses.
How much does semaglutide cost on the NHS vs privately?
On the NHS, semaglutide is free if prescribed through a specialist service, but access is limited and regional variation is significant. Privately, costs range from approximately £129–£200 per month depending on dose and provider. Private prescriptions require an online clinical assessment. Compare the full cost of private treatment with NHS waiting times to decide which route suits you.
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.