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
Wegovy Weight Loss Injection — How It Works in the UK
Wegovy (semaglutide) is a prescription-only weekly injection licensed in the UK for weight management in adults. It works by activating the GLP-1 hormone pathway, which may help reduce appetite and support feeling fuller after smaller meals. Clinical trials showed that Wegovy helped participants lose an average of around 15% of their body weight alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly, and a prescriber will assess whether this medication is suitable for you based on your health profile and BMI. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses.
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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 and What to Expect
Wegovy contains semaglutide, a GLP-1 receptor agonist — a medication that mimics a natural hormone produced in your gut. When you eat, GLP-1 signals to your brain that you're full, slows how quickly food leaves your stomach, and helps regulate blood sugar. Wegovy amplifies these signals, which may reduce hunger and cravings.
The STEP-1 clinical trial found that over 68 weeks, participants taking the maximum 2.4 mg dose lost approximately 14.9% of their body weight on average, compared to about 2.4% in the placebo group. However, results depend on dose, how long you take it, and lifestyle changes you make. Wegovy is injected once weekly under the skin (subcutaneously) — usually in the stomach, thigh, or upper arm. You start on a low dose (0.25 mg) and gradually increase over 16 weeks, reaching the maintenance dose of 2.4 mg.
Important: Wegovy is not insulin and doesn't work the same way. It's designed specifically for weight management and is the licensed version of semaglutide for this purpose — Ozempic is a different formulation approved for type 2 diabetes, not weight loss.
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, Access Routes, and Practical Information
In the UK, you may be eligible for Wegovy 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, abnormal cholesterol, sleep apnoea, or cardiovascular disease. Lower BMI thresholds (27.5 and above) may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, as these groups have higher health risks at lower BMI levels.
Wegovy is available through two routes in the UK: NHS specialist weight management services (tier 3 or 4) via GP referral, though availability and waiting times vary significantly by region; or privately through GPhC-registered online pharmacies following an online clinical assessment. Check your eligibility using our free BMI calculator above, then discuss your options 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.
How much weight can I lose with Wegovy?
Clinical trials showed an average weight loss of around 15% of body weight over 68 weeks at the maximum 2.4 mg dose. However, individual results vary significantly based on dose, duration of use, diet, exercise, and personal factors. Some people lose more, some less. Weight loss typically starts after a few weeks and continues as you progress through dose increases.
What are the main side effects of Wegovy in the UK?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — especially when starting or increasing the dose. These often improve over time. Less common side effects include headache, fatigue, dizziness, and injection site reactions. Serious side effects are rare but seek urgent medical attention for severe stomach pain or allergic reactions.
Is Wegovy available on the NHS in the UK?
Wegovy is available through NHS specialist weight management services in some areas, accessed via GP referral to tier 3 services. However, availability varies significantly by region and waiting lists can be long. Private access through GPhC-registered pharmacies is also available without NHS referral, following an online clinical assessment.
What's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is approved for type 2 diabetes (doses up to 2 mg) and using it for weight loss is off-label in the UK. Wegovy is the licensed weight management version (doses up to 2.4 mg). Wegovy has stronger evidence for weight loss and is the appropriate choice if weight management is your goal.
How often do I inject Wegovy and how do I store it?
Wegovy is injected once weekly, on the same day each week if possible. Unopened pens should be stored in the fridge at 2–8°C in their original carton. After first use, pens can be kept at room temperature (below 30°C) for up to 30 days. Dispose of the pen 30 days after first use. Rotate injection sites between stomach, thigh, and upper arm each week.
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.