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 Used For?
Wegovy is a prescription-only weight management injection licensed in the UK for adults with excess weight or weight-related health conditions. It contains semaglutide, a GLP-1 receptor agonist that works by reducing appetite, helping you feel fuller after eating, and supporting sustainable weight loss alongside dietary changes and physical activity. Wegovy is given as a once-weekly injection and requires a clinical assessment before prescription. It's one of several weight loss medications available in the UK, each with different mechanisms and eligibility criteria.
10,000+ calculations today ยท NHS-aligned thresholds ยท 100% free
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/mยฒ).
While BMI isn't a perfect measure โ it doesn't account for muscle mass, bone density, or fat distribution โ 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 โ 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 It Treats
Wegovy (semaglutide) is a GLP-1 receptor agonist โ meaning it activates a single natural hormone pathway to support weight management. When you eat, your body naturally produces GLP-1, which signals to your brain that you're full. Wegovy amplifies this effect, helping reduce appetite and food cravings.
The injection also slows gastric emptying (how quickly food leaves the stomach), supporting a longer feeling of fullness after smaller meals. In the STEP-1 clinical trial, adults using Wegovy alongside a reduced-calorie diet and increased physical activity lost an average of approximately 14.9% of their body weight โ though individual results vary significantly.
In the UK, Wegovy is prescribed for:
- Adults with a BMI of 30 kg/mยฒ or above (obesity)
- Adults with a BMI of 27โ29.9 kg/mยฒ (overweight) plus at least one weight-related health condition, such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease
- South Asian, Chinese, Black African, or Black Caribbean adults with a BMI of 27 kg/mยฒ or above, due to higher health risks at lower BMI levels
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care โ 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 โ 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 โ completely free.
Wegovy vs Mounjaro: Key Differences
While both Wegovy and Mounjaro are once-weekly weight loss injections licensed in the UK, they work differently. Wegovy is a single GLP-1 receptor agonist, whereas Mounjaro is a dual GIP and GLP-1 receptor agonist, activating two hormone pathways simultaneously. In clinical trials, Mounjaro showed slightly higher average weight loss (15โ21% of body weight) compared to Wegovy (approximately 15%), though both achieved meaningful results. The maximum dose differs: Wegovy reaches 2.4 mg weekly, while Mounjaro goes up to 15 mg weekly. Neither medication is "better" โ suitability depends on your individual health profile, medical history, and how your body responds. Your prescriber will assess which is appropriate for you following a clinical assessment. Use our free GLP-1 weight loss calculator to explore potential outcomes with either medication.
- 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 โ 5mg โ 7.5mg โ 10mg โ 12.5mg โ 15mg
- GLP-1 receptor agonist
- Up to 15โ17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg โ 0.5mg โ 1mg โ 1.7mg โ 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 | 15โ22.5% | 12โ17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20โ32 weeks | 16โ20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | ยฃ150โยฃ250/month | ยฃ150โยฃ300/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 โ 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 prescribed on the NHS in the UK?
Wegovy can be prescribed through NHS specialist tier 3 weight management services, though access varies significantly by region and waiting lists can be lengthy. Private prescribing through online clinical assessments is also available. Either route requires a prescription from a UK-licensed prescriber.
What is the difference between Wegovy and semaglutide?
Wegovy is the branded name for semaglutide 2.4 mg (the weight management dose). Ozempic is also semaglutide but at lower doses (up to 2 mg) and is approved for type 2 diabetes, not weight loss. Wegovy is the licensed weight management version in the UK.
How long does it take to see weight loss results with Wegovy?
Most people begin noticing changes within 2โ4 weeks, with more significant results over 3โ6 months. The dose is increased gradually every 4 weeks, which gives your body time to adjust. Results continue improving over 12โ16 weeks as the dose builds to the maintenance level.
Can I use Wegovy if I'm already taking type 2 diabetes medication?
Possibly, but it requires careful monitoring. Wegovy may interact with diabetes medications like sulphonylureas or insulin, potentially causing low blood sugar. Your prescriber will assess your current medications and may adjust doses. Always inform your healthcare provider of all medications you take.
What happens when you stop taking Wegovy?
Weight can return gradually if diet and lifestyle changes are not maintained. Wegovy is most effective when combined with sustained dietary improvements and physical activity. Your prescriber can discuss long-term management options and whether continued treatment is appropriate for your health goals.
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.