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
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Wegovy Weight Loss Injections in the UK
Wegovy is a prescription-only, once-weekly weight loss injection licensed in the UK for adults with obesity or overweight conditions. It contains semaglutide, a GLP-1 receptor agonist that works by reducing appetite and helping you feel fuller after smaller meals. Clinical trials showed that people using Wegovy lost an average of around 15% of their body weight alongside dietary changes and increased physical activity. Individual results vary significantly, and Wegovy is not suitable for everyone. Your GP or a licensed prescriber can assess whether this weekly weight loss injection is appropriate for your personal health situation.
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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 as a Weight Loss Injection
Wegovy (semaglutide) is a GLP-1 receptor agonist — it mimics a natural hormone your body produces after eating. This helps regulate appetite and food intake through several mechanisms: it signals to your brain that you feel full, slows how quickly food leaves your stomach, and reduces cravings for high-calorie foods.
The medication is injected once weekly under the skin, typically into the stomach, thigh, or upper arm. Unlike daily injections, the once-weekly dosing schedule makes it more convenient for most people. Wegovy is not insulin and does not work the same way as diabetes medications.
In the STEP-1 clinical trial, adults using Wegovy 2.4 mg (the maximum dose) for 68 weeks lost an average of 14.9% of their body weight. However, weight loss results depend on individual factors including diet, exercise, metabolism, and how your body responds to the medication. Use our GLP-1 weight loss calculator to estimate potential weight loss at different doses based on clinical trial data.
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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
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Wegovy Eligibility, Doses, and Side Effects in the UK
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 a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. If you're of South Asian, Chinese, Black African, or Black Caribbean descent, lower BMI thresholds may apply due to higher health risks at lower weights.
Wegovy doses start at 0.25 mg and increase gradually to a maximum of 2.4 mg weekly. Common side effects include nausea, diarrhoea, vomiting, and constipation — most improve over time as your body adjusts. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or allergic reactions; seek immediate medical attention if these occur. Check your BMI using our free BMI calculator to understand your starting point and discuss Wegovy eligibility with your GP or 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 Wegovy and Ozempic contain semaglutide, but they are different medications. Ozempic is licensed for type 2 diabetes (up to 2 mg) and is not approved for weight loss in the UK. Wegovy is licensed specifically for weight management at a higher dose (up to 2.4 mg). Using Ozempic for weight loss would be off-label prescribing. Always ensure your prescriber is giving you Wegovy, not Ozempic, for weight management.
How quickly will I lose weight on Wegovy?
Weight loss on Wegovy varies between individuals. Clinical trials showed an average loss of around 15% of body weight over 68 weeks alongside diet and exercise changes. Some people lose more, some less. Initial weight loss typically becomes noticeable within 4–8 weeks as doses increase. Sustainable weight loss is usually 0.5–1 kg per week. Your prescriber can discuss expected timelines based on your personal health.
How do I access Wegovy in the UK — NHS or private?
Wegovy is available through two routes in the UK. NHS access is through specialist tier 3 weight management services (usually by GP referral), though availability varies by region and waiting lists can be lengthy. Private access is available through online consultations with UK-licensed prescribers followed by dispensing from a GPhC-registered pharmacy. Private costs typically range from £129–£250 per month depending on dose. Ask your GP about NHS options first.
What happens if I stop taking Wegovy?
If you stop Wegovy, appetite regulation typically returns to normal within weeks, and weight loss plateaus. Many people regain some weight after stopping, though not necessarily all of it — this depends on whether lifestyle changes (diet and exercise) are maintained. Wegovy is most effective when used as part of a long-term weight management plan, not as a short-term treatment. Discuss long-term plans with your prescriber before starting.
Can I take Wegovy if I'm taking other medications?
Wegovy may interact with some medications, particularly oral contraceptives (which may be less effective) and diabetes medications (which may need dose adjustment). Always inform your prescriber of all medications, supplements, and medical conditions before starting Wegovy. They will assess whether it's safe to combine with your current treatments and adjust doses if needed. Never start Wegovy without a full clinical assessment.
Ready to take control of your weight loss journey?
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