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 Semaglutide and How Does It Work?
Wegovy is the brand name for semaglutide, a prescription-only injection licensed in the UK specifically for weight management in adults. It works by activating the GLP-1 hormone pathway, which helps reduce appetite, support feeling fuller after smaller meals, and slow how quickly food leaves your stomach. Clinical trials showed that alongside a reduced-calorie diet and increased physical activity, semaglutide weight loss results averaged around 15% of body weight over 68 weeks — though individual results vary significantly. Unlike Ozempic (which is also semaglutide but approved for type 2 diabetes), Wegovy is the licensed weight management version in the UK.
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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 Semaglutide Works and What to Expect
Mechanism: Semaglutide is a GLP-1 receptor agonist, meaning it mimics and amplifies a natural gut hormone called GLP-1 (glucagon-like peptide-1). When activated, this pathway signals to your brain that you are full, reduces food cravings, and slows gastric emptying — how quickly food moves through your digestive system.
- Appetite reduction: May help you feel satisfied with smaller portions
- Craving control: Evidence suggests reduced desire for high-calorie foods
- Metabolic support: Supports your body's natural appetite regulation
Wegovy is administered as a once-weekly injection. Treatment typically starts at a low dose (0.25 mg) and increases gradually over several weeks to reach the maintenance dose of 2.4 mg. This gradual escalation helps your body adapt and reduces nausea. You can check your projected weight loss outcomes using our free GLP-1 weight loss calculator to understand potential results at different doses.
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.
Eligibility, Doses and Side Effects in the UK
UK eligibility: Adults with a BMI of 30 or above, or 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease), may be eligible for Wegovy. Use our free BMI calculator to check where you fall on the NHS healthy weight scale.
Common side effects: Most frequent are nausea, diarrhoea, constipation, and stomach pain — these typically ease as your body adjusts. Less common side effects include headache, fatigue, and injection site reactions. Serious side effects are rare but require immediate medical attention: severe abdominal pain (possible pancreatitis), gallbladder problems, or serious allergic reactions. Always inform your prescriber of all existing health conditions and medications before starting treatment.
- 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 semaglutide?
Both contain semaglutide but serve different purposes. Ozempic is licensed for type 2 diabetes (up to 2 mg dose) and is not approved for weight loss in the UK. Wegovy is the licensed weight management version (up to 2.4 mg). Using Ozempic for weight loss is off-label and not recommended. Always ask your prescriber which version is appropriate for you.
How much weight can I expect to lose with Wegovy?
Clinical trials (STEP-1) showed an average weight loss of approximately 15% of body weight over 68 weeks on the maximum 2.4 mg dose, alongside diet and exercise. Individual results vary significantly — some people lose more, some less. Weight loss depends on your starting weight, adherence, diet, and activity level. Results are not assured.
How do I access Wegovy in the UK — NHS or private?
NHS access requires referral to a specialist tier 3 weight management service through your GP. Availability and waiting times vary by region. Private access is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Private options are typically faster but involve costs of approximately £129–£250 per month depending on dose.
What are the main side effects of Wegovy semaglutide?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain. These typically reduce within the first few weeks as your body adjusts. Less common effects include headache, fatigue, and dizziness. Serious side effects (severe abdominal pain, gallbladder problems, severe allergic reactions) are rare but require immediate medical attention. Report all side effects to your prescriber.
Is Wegovy covered by the NHS in the UK?
Yes, semaglutide (generic name) was approved by NICE for use within NHS specialist weight management services. However, NHS access is through tier 3 specialist services, not standard GP prescription, and availability varies significantly by region. Many areas have substantial waiting lists. Private access is available without NHS referral if you meet eligibility criteria and obtain a prescription from 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.