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 Reviews — Evidence-Based Outcomes
Semaglutide (Wegovy) is a prescription-only weekly weight loss injection licensed in the UK. This guide breaks down what real clinical evidence shows about weight loss outcomes, how it works, and what you can realistically expect. We explain the difference between Wegovy and Ozempic, review trial data, and answer key questions about this GLP-1 receptor agonist medication. All individual results vary — this is educational information only.
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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.
What the Clinical Evidence Shows About Semaglutide Weight Loss
Semaglutide weight loss reviews are based primarily on the STEP clinical trials, the largest evidence pool for this medication. In the STEP-1 trial, adults taking semaglutide 2.4 mg (the maximum Wegovy dose) lost an average of 14.9% of their body weight over 68 weeks — significantly more than the placebo group, who lost approximately 2.4% on average.
- STEP-1 trial: 14.9% average weight loss at 2.4 mg dose alongside a reduced-calorie diet and increased physical activity
- Lower doses: Results at 1 mg and 1.7 mg were proportionally lower — typically 9–clinically studied weight loss
- Time to results: Weight loss typically began in weeks 4–8 and continued progressively
Important context: These are trial averages. Individual outcomes vary significantly based on genetics, lifestyle adherence, starting weight, and overall health. Some people lose more; some lose less. Results require both the medication and sustained lifestyle changes — diet and activity alone without the injection don't produce these figures.
Clinically BackedWeight Loss
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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.
How Semaglutide Works and Why Reviews Matter
Semaglutide is a GLP-1 receptor agonist — it mimics a natural gut hormone that signals fullness to your brain. This mechanism helps reduce appetite, food cravings, and portion sizes. Unlike Ozempic (which is approved for type 2 diabetes at lower doses), Wegovy is specifically licensed for weight management in UK adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions like high blood pressure or prediabetes.
Reviews often highlight that results are not assured — they depend on consistent use, dose tolerance, and lifestyle commitment. Some people experience reduced appetite immediately; others take several weeks to notice effects. Our free GLP-1 weight loss calculator can help you explore potential outcomes at different doses based on trial data.
Side effects commonly mentioned in reviews include nausea (especially weeks 1–4 on a new dose), diarrhoea, and constipation. These typically improve over time. More serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder problems. Any concerns should be discussed with your prescriber immediately. Track your progress and side effect patterns using our free progress tracker to share with your GP or private prescriber.
- 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.
Is semaglutide weight loss permanent after you stop?
No. When you stop semaglutide, appetite typically returns to baseline and weight regain is common. Most people regain weight without continued lifestyle changes. This is why sustainable diet and activity habits are essential during treatment. Your prescriber can discuss long-term management strategies.
How does semaglutide compare to Ozempic for weight loss?
Both contain the same active ingredient, but Ozempic is licensed for type 2 diabetes (doses up to 2 mg) and is not approved for weight loss in the UK. Wegovy is the licensed weight management version (doses up to 2.4 mg). Using Ozempic for weight loss off-label is not recommended — Wegovy is the appropriate licensed choice.
What's the difference between semaglutide and tirzepatide (Mounjaro)?
Semaglutide is a GLP-1 agonist; tirzepatide is a dual GIP + GLP-1 agonist. Clinical trials show tirzepatide may produce slightly higher average weight loss (15–21% vs 14.9% for semaglutide), but both require prescription and clinical assessment. Individual responses vary significantly.
Can I get semaglutide (Wegovy) on the NHS in the UK?
NHS access is through specialist tier 3 weight management services by GP referral. Availability varies significantly by region and waiting times can be months to years. Private prescription is available through licensed online prescribers following a clinical assessment, typically at faster access.
How quickly do you lose weight on semaglutide?
Most people notice initial weight loss in weeks 4–8, with progressive loss continuing over months. The average trial timeline was 68 weeks for full results. Rate varies by dose, individual metabolism, and lifestyle adherence. Use our BMI calculator to establish your current baseline, then track changes over time with our progress tracker.
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.