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 Injections — What You Need to Know
Wegovy injections are a prescription-only weight management medicine licensed in the UK for adults with obesity or overweight with related health conditions. This once-weekly GLP-1 receptor agonist injection may help reduce appetite and support weight loss alongside diet and physical activity. Understanding how Wegovy works, the doses available, eligibility criteria, and what to expect can help you have an informed conversation with your GP or healthcare provider about whether this treatment might be suitable for you.
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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 What to Expect
Wegovy (semaglutide) is a GLP-1 receptor agonist — this means it activates the GLP-1 hormone pathway, which naturally helps regulate appetite and blood sugar. When you take Wegovy, it signals to your brain that you feel fuller, may reduce cravings for food, and slows how quickly food leaves your stomach. This can help you eat smaller portions and feel satisfied with less food.
Treatment typically starts at a low dose and increases gradually over weeks to find the right level for you. Clinical trials (the STEP programme) showed that adults on Wegovy lost an average of approximately 15% of their body weight over 68 weeks — though individual results vary significantly. You use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, based on clinical trial data.
- Wegovy is a once-weekly injection you administer yourself using a pre-filled pen
- It is prescription-only and requires a clinical assessment before being prescribed
- It works best alongside a reduced-calorie diet and increased physical activity
- Results are not assured — weight loss depends on your individual metabolism and lifestyle changes
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 Access 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 weight-related health conditions 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 lower BMI thresholds because these groups face higher health risks at the same BMI level. Check your personal BMI using our free BMI calculator above.
Wegovy doses range from 0.25 mg (starting) to 2.4 mg (maximum), increased gradually over 16+ weeks. In the UK, you can access Wegovy either through NHS specialist weight management services (with a GP referral and potential waiting lists) or through private online prescribing with GPhC-registered pharmacies. Both routes require a clinical assessment. Your prescriber will confirm whether Wegovy vs Mounjaro (the alternative GIP/GLP-1 injection) is more appropriate for your circumstances.
- 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 licensed for type 2 diabetes (doses up to 2 mg) and is not approved for weight loss in the UK. Wegovy is the licensed weight management version with higher doses up to 2.4 mg. Using Ozempic for weight loss would be off-label. Always use the medication specifically prescribed for you.
What are the most common side effects of Wegovy?
Very common side effects include nausea, diarrhoea, vomiting, and constipation, especially when starting or increasing doses. Mild stomach pain and indigestion are also frequent. Most side effects improve over time. Seek urgent medical attention for severe, persistent stomach pain (possible pancreatitis) or serious allergic reactions.
How long does Wegovy take to work?
Weight loss typically begins within the first 4–8 weeks, though some people notice appetite reduction sooner. Maximum effectiveness is usually reached by week 16–20 when you reach the maintenance dose of 2.4 mg. Individual timelines vary — your prescriber can discuss realistic expectations for you.
Can I get Wegovy on the NHS in the UK?
Yes, Wegovy is available through NHS specialist weight management services. You'll need a GP referral to a tier 3 or tier 4 service. Availability and waiting times vary significantly by region. Your local Integrated Care Board (ICB) determines access. Private online prescribing is also available without NHS referral.
What happens if I miss a dose of Wegovy?
If you miss a dose, take it within 4 days of the scheduled time and continue your normal schedule. If more than 4 days have passed, skip that dose and take your next dose on the usual day. Never take a double dose. Doses must be at least 3 days (72 hours) apart.
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.