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 Injection?
Wegovy is a prescription-only weekly injection containing semaglutide, a medication licensed in the UK for weight management in adults. It works by mimicking a natural hormone that helps regulate appetite and blood sugar, potentially supporting weight loss when combined with diet and exercise changes. This guide explains how Wegovy works, who it's suitable for, what to expect, and how it compares to other weight loss treatments available 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 Works and What It Contains
Wegovy is a GLP-1 receptor agonist — a type of medication that activates the glucagon-like peptide-1 (GLP-1) hormone pathway in your body. This natural hormone is normally released after eating and signals to your brain that you feel full, slows stomach emptying, and helps regulate blood sugar levels.
- The active ingredient is semaglutide, manufactured by Novo Nordisk
- It's administered as a once-weekly injection using a pre-filled pen
- Doses range from 0.25 mg to 2.4 mg, gradually increased over 17 weeks
- Licensed in the UK specifically for weight management (unlike Ozempic, which contains semaglutide at lower doses for diabetes only)
- In clinical trials (STEP-1), participants lost an average of 14.9% of their body weight at 68 weeks — though individual results vary significantly
Wegovy may help reduce food cravings, support feeling fuller after smaller meals, and decrease overall appetite. Results are achieved alongside a reduced-calorie diet and increased physical activity.
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.
Wegovy Eligibility and How to Access It 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 at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply. Access routes differ: NHS access is through specialist tier 3/4 weight management services following GP referral, though waiting lists can be lengthy. Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. Try our GLP-1 weight loss calculator to explore potential outcomes, and use the BMI calculator to check your current status against NHS thresholds.
- 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 contain semaglutide, but they are different medicines. Ozempic is approved for type 2 diabetes (doses up to 2 mg) and is not licensed for weight loss in the UK. Wegovy is specifically licensed for weight management (doses up to 2.4 mg). Using Ozempic for weight loss is off-label use.
How quickly does Wegovy start working?
Weight loss typically begins within the first few weeks, though most significant loss occurs after 12–16 weeks as your dose increases. The STEP-1 trial measured weight loss over 68 weeks. Results vary between individuals — some lose weight faster than others.
What are the main side effects of Wegovy in the UK?
Common side effects include nausea, diarrhoea, constipation, vomiting, and stomach pain — especially during dose increases. Most settle within days to weeks. Serious side effects are rare but can include pancreatitis (severe stomach pain) and gallbladder problems. Always inform your GP of any concerning symptoms.
How is Wegovy different from Mounjaro?
Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist — it activates two hormone pathways. Clinical trial data suggests Mounjaro may produce slightly larger average weight loss, but individual results vary significantly. Both are once-weekly injections.
Do I need to stay on Wegovy forever?
Wegovy is intended as a long-term treatment. If you stop taking it, weight often returns over time. Your GP or prescriber will discuss the best approach for your individual situation — some people may pause or stop treatment, while others continue long-term alongside lifestyle changes.
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.