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 Weight Loss Jab Explained
Wegovy is a prescription-only weekly weight loss injection licensed in the UK for adults with obesity or overweight with weight-related health conditions. The active ingredient is semaglutide, a GLP-1 receptor agonist that works by reducing appetite and helping you feel fuller after eating. Clinical trials showed Wegovy helped people lose an average of around 15% of their body weight, though individual results vary significantly. It's used alongside a reduced-calorie diet and increased physical activity for best results.
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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 and Dosing Schedule
Wegovy contains semaglutide, which activates GLP-1 receptors in the brain and gut. This single mechanism helps regulate appetite signals, slows how quickly food leaves the stomach, and supports feeling satisfied with smaller meal portions. The STEP-1 clinical trial demonstrated an average weight loss of approximately 14.9% body weight over 68 weeks when combined with lifestyle changes.
Wegovy starts at a low dose and gradually increases over several months:
- Weeks 1–4: 0.25 mg once weekly
- Weeks 5–8: 0.5 mg once weekly
- Weeks 9–12: 1 mg once weekly
- Weeks 13–16: 1.7 mg once weekly
- Week 17+: 2.4 mg once weekly (maximum maintenance dose)
Each dose is injected under the skin once per week, typically in the stomach, thigh, or upper arm. Try our GLP-1 weight loss calculator to estimate potential weight loss at different doses based on clinical data.
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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.
Eligibility, Access, and What to Expect
In the UK, you may be eligible for Wegovy if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have access at lower BMI thresholds due to higher health risks at lower weights.
Wegovy is available through NHS specialist weight management services (though availability and waiting times vary by region) or through private online prescribing following a clinical assessment. Common side effects include nausea, diarrhoea, vomiting, and constipation—most people find these improve over time. Check your BMI using our free BMI calculator to see where you fall, and discuss Wegovy eligibility with your GP or a licensed 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 Wegovy the same as Ozempic?
Both contain semaglutide, but they're different products. Ozempic is licensed for type 2 diabetes (doses up to 2 mg). Wegovy is the licensed weight management version (doses up to 2.4 mg). Using Ozempic for weight loss would be off-label. Always use the licensed medication as prescribed.
How much weight will I lose on Wegovy?
Clinical trials showed an average weight loss of around 15% of body weight, but individual results vary significantly. Some people lose more, some less. Weight loss depends on your starting weight, adherence to diet and exercise, genetics, and how your body responds to the medication. Your prescriber can discuss realistic expectations.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 receptor agonist. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist—it activates two hormone pathways instead of one. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but both are effective. Your prescriber will advise which is more suitable.
Can I get Wegovy on the NHS?
Wegovy is available through NHS tier 3 specialist weight management services, but access varies significantly by region and there can be long waiting lists. NICE has approved it for NHS use. Alternatively, Wegovy is available privately through UK-licensed online prescribers following a clinical assessment.
What happens if I stop taking Wegovy?
Weight loss is typically maintained through ongoing lifestyle changes (diet and exercise). If you stop the injection without sustaining these changes, weight may gradually return. Wegovy is a tool to support weight loss, not a permanent supports. Discuss long-term plans with your prescriber before stopping 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.