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
What Is Wegovy? The Complete Guide
Wegovy is a prescription-only weight management injection licensed in the UK for adults with obesity or overweight with weight-related health conditions. It contains semaglutide, a GLP-1 receptor agonist — a medication that mimics a natural gut hormone to help reduce appetite and support weight loss alongside diet and exercise. Wegovy is different from Ozempic, which is also semaglutide but approved only for type 2 diabetes, not weight loss. This guide explains how Wegovy works, UK eligibility, doses, and what to expect.
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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 Wegovy Works: The Mechanism
Wegovy activates the GLP-1 receptor, which is part of your body's natural appetite regulation system. When you eat, your gut naturally releases GLP-1 hormone, which signals to your brain that you're full. Wegovy mimics and amplifies this effect, helping you feel satisfied with smaller portions and experience fewer food cravings.
The medication also slows gastric emptying — how quickly food leaves your stomach — which extends the feeling of fullness after meals. This combined effect may help you eat less overall without feeling deprived. Clinical trials (the STEP-1 trial) showed that participants taking semaglutide lost an average of approximately 14.9% of their body weight over 68 weeks, though individual results vary significantly. Wegovy is always used alongside a reduced-calorie diet and increased physical activity — it's not a standalone solution.
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.
UK Eligibility and How to Access Wegovy
In the UK, Wegovy may be prescribed for adults with a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at slightly lower BMI thresholds due to higher health risks at lower weights.
You can access Wegovy through NHS specialist weight management services (tier 3/4) via GP referral, though waiting lists vary significantly by region. Alternatively, private online prescribing is available — you'll have an online consultation with a UK-licensed prescriber, and if approved, your prescription is dispensed by a GPhC-registered pharmacy. Use our free GLP-1 weight loss calculator to explore potential weight loss at different doses, and check your BMI using our free BMI calculator to assess your starting point.
- 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?
Both contain semaglutide, but they're different medicines. Ozempic is approved for type 2 diabetes (doses up to 2mg). Wegovy is the weight loss version, licensed specifically for weight management with a higher maximum dose of 2.4mg. Ozempic should not be used for weight loss in the UK — Wegovy is the licensed option.
What dose of Wegovy would I start on?
The starting dose is 0.25mg once weekly. You increase gradually every 4 weeks: 0.5mg, then 1mg, then 1.7mg, and finally 2.4mg (the maximum dose). Your prescriber decides the pace based on tolerability and results. Most people reach the 2.4mg maintenance dose around week 17.
How much weight can I expect to lose with Wegovy?
Clinical trials showed average weight loss of around 14.9% of body weight, but this varies widely between individuals. Some people lose more, some less. Weight loss depends on your starting weight, how well you stick to a reduced-calorie diet, physical activity, and how your body responds to the medication. Results are never assured.
What are the most common Wegovy side effects?
Very common side effects include nausea, diarrhoea, vomiting, and constipation — especially when starting or increasing doses. These usually improve over time. Less common side effects are fatigue, dizziness, and injection site reactions. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder problems — seek immediate medical attention if these occur.
Can I get Wegovy on the NHS in the UK?
Yes, Wegovy can be prescribed through NHS specialist weight management services (tier 3/4), but access varies significantly by region and local waiting lists can be very long. Your GP can refer you to your local specialist service. Private prescribing is also available and typically faster — you'll need an online clinical assessment with a UK-licensed prescriber.
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.