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 Treatment: How This GLP-1 Injection Works
Wegovy treatment is a prescription-only, once-weekly injection containing semaglutide — a GLP-1 receptor agonist licensed in the UK for weight management in adults. It works by activating natural appetite-regulating hormones in your gut, helping you feel fuller after smaller meals and reducing food cravings. Clinical trials showed that Wegovy helped participants lose an average of around 15% of their body weight over 68 weeks, though individual results vary significantly. Wegovy is different from Ozempic, which also contains semaglutide but is licensed for type 2 diabetes, not weight loss. This guide covers how Wegovy treatment works, eligibility criteria, doses, side effects, and how to access it in the UK.
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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 is a GLP-1 receptor agonist — it mimics and amplifies the natural hormone GLP-1 (glucagon-like peptide-1), which your gut produces after eating. This hormone signals to your brain that you are full, helping reduce hunger and appetite. Wegovy may also slow how quickly food leaves your stomach, helping you feel satisfied longer after meals.
Wegovy treatment typically begins with a starting dose of 0.25 mg once weekly, then gradually increases over 16+ weeks to a maximum of 2.4 mg weekly. Each increase gives your body time to adjust and minimises nausea. According to the STEP-1 clinical trial, the average weight loss was approximately 14.9% of body weight at the 2.4 mg maintenance dose, alongside reduced-calorie diet and increased physical activity. However, results vary — some people lose more, others less.
Weight loss with Wegovy treatment usually becomes noticeable around weeks 4–8, with most weight loss occurring between weeks 8–20. It is important to combine Wegovy with lifestyle changes for best results.
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 and How to Access Wegovy in the UK
You may be eligible for Wegovy treatment in the UK if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with a weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or heart disease. Lower BMI thresholds (27.5+) apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage — these groups face higher health risks at lower weights.
NHS access: Through tier 3 specialist weight management services. Availability varies significantly by region; waiting lists can be several months to years.
Private access: Via online consultation with a UK-licensed prescriber and GPhC-registered pharmacy. Available without NHS referral; no waiting lists but costs around £129–£320 monthly depending on dose. A prescriber will assess whether Wegovy treatment is suitable for you based on your medical history and current health.
- 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 Wegovy is licensed specifically for weight management (up to 2.4 mg). Using Ozempic for weight loss is off-label use. Wegovy is the prescription-only licensed weight loss version of semaglutide in the UK.
How quickly will I lose weight with Wegovy treatment?
Weight loss typically becomes noticeable in weeks 4–8, with most loss occurring weeks 8–20. Average loss is around 15% of body weight over 68 weeks in clinical trials, but individual results vary significantly. You lose weight fastest alongside a reduced-calorie diet and increased physical activity.
What are the main side effects of Wegovy treatment?
Very common side effects include nausea, diarrhoea, constipation, and stomach pain — usually mild and reduce over time. Less common: headache, fatigue, dizziness, and injection site reactions. Serious side effects (rare) include severe stomach pain (possible pancreatitis) and serious allergic reactions. Contact your GP immediately if you experience severe symptoms.
Can I use Wegovy treatment on the NHS?
Yes, but availability is limited and varies significantly by region. You need referral to a tier 3 specialist weight management service through your GP. Waiting times can be very long. Private access is available through online prescribing without NHS referral, though this involves a cost. Your local integrated care board (ICB) determines NHS availability in your area.
What dose of Wegovy treatment will I start on?
Wegovy treatment begins at 0.25 mg weekly, increasing every 4 weeks: 0.25 mg → 0.5 mg → 1 mg → 1.7 mg → 2.4 mg (maximum). Your prescriber may adjust the pace based on how you tolerate each dose. The 2.4 mg maintenance dose is typically reached around week 17. You take one injection once per 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.