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 Wegovy Supports Weight Loss
Wegovy (semaglutide) is a prescription-only weekly injection that may help support weight loss in UK adults. Clinical trials showed Wegovy helped participants lose an average of around 15% of their body weight over 68 weeks when used alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly. Wegovy works by activating the GLP-1 hormone pathway, which helps reduce appetite, support feeling fuller after smaller meals, and slow how quickly food leaves the stomach. It's only available on prescription following a clinical assessment to check eligibility.
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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.
How Wegovy Works for Weight Loss
Wegovy contains semaglutide, a GLP-1 receptor agonist — a medication that mimics a natural gut hormone produced after eating. This hormone signals to your brain that you're full, stimulates insulin release, and slows gastric emptying (how quickly food leaves your stomach).
The GLP-1 mechanism may help you:
- Feel less hungry between meals
- Experience reduced food cravings
- Feel fuller after eating smaller portions
- Have better control over eating habits
In the STEP-1 clinical trial, participants on Wegovy 2.4 mg (the maximum dose) lost an average of 14.9% of their body weight over 68 weeks. However, weight loss varies — some people lose more, some less. Results are achieved alongside dietary changes and increased physical activity, not through the injection alone. Unlike oral diabetes medication, Wegovy is injected once weekly under the skin.
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 & How to Access Wegovy
You may be eligible for prescription Wegovy in the UK if you have 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). Use our free BMI calculator above to check your current BMI instantly.
Access routes in the UK:
- NHS: Referral to specialist weight management services (tier 3) — significant waiting lists in many areas; availability varies by region
- Private: Online consultation with a UK-licensed prescriber — faster access without NHS referral; costs typically £129–£320 monthly depending on dose
A licensed prescriber will assess your medical history, current medications, and health conditions before prescribing. Try our GLP-1 weight loss calculator to estimate potential weight loss 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 Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is approved for type 2 diabetes (up to 2 mg dose) and is not licensed for weight loss in the UK. Wegovy is specifically approved for weight management (up to 2.4 mg dose). Using Ozempic for weight loss is off-label. Wegovy is the correct licensed option for weight management.
How much weight will I lose on Wegovy?
Clinical trials showed average weight loss of around 15% of body weight over 68 weeks on Wegovy 2.4 mg. Individual results vary significantly — some lose more, some less. Weight loss depends on your starting weight, dose, adherence, and lifestyle changes. Results are not assured and require a reduced-calorie diet and increased physical activity.
How often do I inject Wegovy?
Wegovy is a once-weekly injection. You inject the same dose every 7 days under your skin on your stomach, thigh, or upper arm. Each pre-filled pen contains 4 weeks of doses. You rotate injection sites to avoid skin irritation.
What are the most common Wegovy side effects?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — typically mild and improve over time as your body adjusts. Less common: headache, fatigue, dizziness, and injection site reactions. Serious side effects are rare but include severe stomach pain (possible pancreatitis) — contact your GP immediately if this occurs.
Can I get Wegovy on the NHS?
Yes, Wegovy is available on the NHS through specialist weight management services (tier 3). However, access is limited and waiting lists can be very long depending on your region and local commissioning. Private prescription routes offer faster access without NHS referral. Track your weight loss progress using our free progress tracker once you begin treatment.
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.