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
How Does Wegovy Work for Weight Loss?
Wegovy is a prescription-only weekly weight loss injection containing semaglutide, a GLP-1 receptor agonist. It works by mimicking a natural gut hormone that signals fullness to your brain, helping reduce appetite and food cravings. In the UK, Wegovy is licensed for weight management and prescribed through NHS specialist services or private online prescribing. Understanding how this weekly weight loss injection works can help you make an informed decision about whether it's right for you, alongside lifestyle changes and clinical assessment.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
How the GLP-1 Mechanism Works
Wegovy (semaglutide) is a GLP-1 receptor agonist — it activates the same natural hormone pathway your gut uses after eating. Here's how it works:
- Appetite suppression: GLP-1 signals to your brain's appetite centres, reducing hunger and food cravings.
- Increased satiety: You feel fuller after smaller meals, naturally eating less.
- Slowed digestion: Semaglutide slows how quickly food leaves your stomach, prolonging the feeling of fullness.
- Blood sugar control: It helps regulate glucose levels, supporting stable energy and reduced cravings.
Clinical trials showed this approach helps participants lose an average of approximately 14.9% of their body weight over 68 weeks — though individual results vary significantly. Weight loss is achieved by creating a calorie deficit: with reduced appetite and increased satiety, many people naturally consume fewer calories without strict dieting. Wegovy is not insulin and works entirely differently from diabetes medications.
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.
NHS Access and Eligibility in the UK
In the UK, you may be eligible for Wegovy through NHS tier 3 specialist weight management services if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. However, NHS access is limited and varies significantly by region — waiting lists can be substantial in many areas. Alternatively, Wegovy is available privately through UK-licensed online prescribers following a clinical assessment, without NHS referral. Check your BMI using our free BMI calculator to see where you stand, then discuss eligibility with your GP or a qualified prescriber. Both routes require a prescription and ongoing clinical 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.
Is Wegovy the same as Ozempic?
No. Ozempic and Wegovy both contain semaglutide, but Ozempic is licensed for type 2 diabetes management (up to 2 mg), while Wegovy is licensed specifically for weight management (up to 2.4 mg). Using Ozempic for weight loss is off-label in the UK. Wegovy is the licensed weight loss version.
How long does it take to see weight loss results with Wegovy?
Most people begin noticing appetite reduction within the first 1–2 weeks. However, measurable weight loss typically becomes evident after 4–8 weeks of consistent use. The STEP clinical trials measured significant weight loss over 68 weeks, so patience and adherence are important for sustained results.
What dose of Wegovy do I start on?
Wegovy starts at 0.25 mg weekly, increasing gradually to 0.5 mg, 1 mg, 1.7 mg, and finally 2.4 mg (the maximum dose). Each dose is used for a minimum of 4 weeks before increasing. Your prescriber will adjust based on your response and tolerance.
Can I get Wegovy on the NHS in my area?
NHS availability of Wegovy is limited and varies significantly by region and ICB (Integrated Care Board). Your GP can refer you to your local tier 3 weight management service to check eligibility and waiting lists. Private prescribing offers faster access without NHS referral.
What's the difference between Wegovy and Mounjaro for weight loss?
Wegovy (semaglutide) is a single GLP-1 agonist, while Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist — activating two hormone pathways instead of one. Clinical trials showed similar average weight loss (14–21%), but individual response varies. A prescriber can advise which is more suitable for 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.