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 Doses For Weight Loss — What You Need to Know
Semaglutide is a prescription-only GLP-1 receptor agonist licensed in the UK for weight management in adults. It's available under the brand name Wegovy, and comes in gradually increasing doses over several months. Understanding how semaglutide doses work — what they are, how they're increased, and what clinical trials showed — can help you make informed decisions about whether this weight loss injection might be right for you. This guide covers the complete dose schedule, mechanism, and expected outcomes based on NHS-approved evidence.
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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.
How Semaglutide Doses Work — The Treatment Schedule
Semaglutide for weight loss is administered as a once-weekly injection, with doses gradually increased over approximately 16 weeks. This stepped approach allows your body to adapt and helps minimise side effects. The dose escalation follows this pattern: 0.25 mg (weeks 1–4), 0.5 mg (weeks 5–8), 1 mg (weeks 9–12), 1.7 mg (weeks 13–16), and finally 2.4 mg (week 17 onwards) as the maintenance and maximum dose.
Each dose is injected once weekly on the same day. The 2.4 mg maintenance dose is the highest dose used in the UK for weight loss — this is where most patients continue long-term. Important note: Ozempic also contains semaglutide but is approved for type 2 diabetes at lower doses (up to 2 mg) and is not licensed for weight loss; Wegovy is the specifically licensed weight management version.
Use our GLP-1 weight loss calculator to see how different semaglutide doses may affect potential weight loss outcomes based on clinical trial data.
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Clinical Trial Results — What Weight Loss Can You Expect?
The STEP-1 clinical trial demonstrated that semaglutide at the 2.4 mg dose led to an average weight loss of approximately 14.9% of body weight over 68 weeks in adults without type 2 diabetes. This was significantly greater than the placebo group. Individual results vary considerably — some participants lost more, others less — and results were achieved alongside a reduced-calorie diet and increased physical activity.
Try our BMI calculator to check your current health status and understand your starting point. Lower doses (0.5 mg to 1.7 mg) typically produce progressive weight loss as you escalate, but the greatest effect is usually seen at the 2.4 mg maintenance dose. Weight loss is not assured, and some people may find they reach a plateau or that semaglutide is not suitable for them following clinical assessment.
- 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 semaglutide and how does it work for weight loss?
Semaglutide is a GLP-1 receptor agonist — a prescription-only injectable medication that mimics the natural gut hormone GLP-1. It works by reducing appetite, helping you feel fuller after smaller meals, and slowing gastric emptying. Wegovy is the UK-licensed brand name for semaglutide specifically for weight management. It's not insulin and works differently from diabetes medications.
How long does it take to reach the full 2.4 mg dose?
It takes approximately 16 weeks (4 months) of gradual dose increases to reach the 2.4 mg maintenance dose. You start at 0.25 mg and increase every 4 weeks. This stepped approach allows your body to adapt and helps reduce gastrointestinal side effects. Your prescriber may adjust the timeline based on your individual tolerance.
What weight loss results did clinical trials show?
The STEP-1 trial showed that semaglutide 2.4 mg resulted in average weight loss of about 14.9% of body weight over 68 weeks — alongside lifestyle changes. Individual results vary significantly. Lower doses produced less weight loss than the full 2.4 mg dose. Results are not assured and depend on adherence, diet, and physical activity.
Can you take semaglutide at a lower dose indefinitely, or do you have to reach 2.4 mg?
Your prescriber decides the appropriate dose for you during clinical assessment. Some people may remain on lower doses if they're achieving good results and tolerating the medication well. However, 2.4 mg is the licensed maintenance dose for weight loss in the UK, and most people progress to this if tolerated, as clinical trials showed the greatest effect at this dose.
Is semaglutide (Wegovy) the same as Ozempic?
Both contain semaglutide, but they're different products. Wegovy is licensed specifically for weight management and uses doses up to 2.4 mg. Ozempic is licensed for type 2 diabetes and uses doses up to 2 mg. Using Ozempic for weight loss would be off-label. Always ensure your prescription specifies Wegovy if weight loss is your goal.
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.