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
How Effective Is Wegovy for Weight Loss?
Wegovy (semaglutide) is a prescription-only GLP-1 receptor agonist injection licensed in the UK for weight management. Clinical trials showed it can be effective for many people, but results vary significantly. This guide explains the evidence behind Wegovy's effectiveness, how it works, what the STEP trial data actually showed, and whether it may be suitable for you. We'll also help you understand how Wegovy compares to other weight loss options and what realistic expectations look like.
10,000+ calculations today · NHS-aligned thresholds · 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/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.
What the Clinical Evidence Shows About Wegovy
Wegovy's effectiveness is supported by the STEP clinical trial programme. In STEP-1, participants taking 2.4 mg semaglutide (the maximum UK dose) lost an average of approximately 14.9% of their body weight over 68 weeks, alongside a reduced-calorie diet and increased physical activity. This means someone weighing 100 kg might lose around 15 kg on average — though individual results vary considerably.
It's crucial to understand that this is an average across all trial participants. Some people lost significantly more weight; others lost less. The semaglutide works as a GLP-1 receptor agonist, meaning it mimics a natural hormone that signals fullness to the brain, reduces appetite, and slows gastric emptying. However, effectiveness depends on several factors: your starting weight, metabolism, adherence to the injection schedule, dietary choices, physical activity level, and individual body response.
- Average weight loss in trials: 14.9% of body weight at maximum dose
- Alongside lifestyle changes: diet and exercise are essential for best results
- Individual variation: results range from modest to significant loss
- Time frame: results shown over 68 weeks, not immediate
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 Effectiveness vs Other Weight Loss Methods
Compared to a calorie-restricted diet alone, Wegovy has shown greater average weight loss in clinical trials. A typical calorie deficit of 500 kcal daily produces roughly 0.5 kg per week loss (around 26 kg per year), whereas Wegovy participants averaged greater losses. When compared to Mounjaro (tirzepatide), a newer GLP-1 medication, Mounjaro showed slightly higher average weight loss in SURMOUNT trials (around 20.9% at maximum dose vs Wegovy's 14.9%), though both are effective options.
The key factor determining effectiveness isn't just the medication — it's consistent use alongside lifestyle changes. Wegovy is a UK prescription-only medicine requiring clinical assessment, and it's most effective when combined with reduced-calorie eating and regular physical activity. Many people find that once they start Wegovy, they naturally make better food choices because appetite reduction makes portion control easier.
Use our free GLP-1 weight loss calculator to estimate potential weight loss at different Wegovy doses based on your current weight. You can also check your current BMI using our free BMI calculator to see whether you fall within the UK eligibility criteria for prescription weight loss treatment (BMI 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease).
- 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.
Does Wegovy work for everyone?
No. While clinical trials showed Wegovy is effective on average, individual results vary significantly. Some people lose substantial weight; others see modest results. Effectiveness depends on genetics, metabolism, medication adherence, diet, exercise, and how your body responds to semaglutide. Your GP or prescriber can discuss realistic expectations for your situation.
Is Wegovy the same as Ozempic?
Both contain semaglutide, but they are different products. Ozempic is licensed for type 2 diabetes (doses up to 2 mg). Wegovy is the licensed weight management version (doses up to 2.4 mg). Ozempic is not approved for weight loss in the UK — Wegovy is the correct prescription for weight management.
How long does it take to see results from Wegovy?
Most people begin noticing appetite reduction within 1–2 weeks of starting. Measurable weight loss typically appears within 4–8 weeks. Significant weight loss (5–10% of body weight) usually takes 12–16 weeks. The STEP trial measured results over 68 weeks, so patience and consistency are important.
Can I stop taking Wegovy once I've lost weight?
This requires discussion with your prescriber. Some people maintain weight loss after stopping; others regain weight. Wegovy is often used as part of long-term weight management rather than a short-term course. Your GP can advise on the best approach for your health goals.
What makes Wegovy more or less effective than diet alone?
Wegovy reduces hunger and increases fullness signals, making it easier to stick to a calorie deficit without constant willpower. Diet alone requires sustained effort against your natural appetite. Wegovy addresses the biological mechanisms driving hunger, which is why clinical trials showed greater average weight loss compared to lifestyle changes alone.
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.