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
Is Wegovy Good For Weight Loss?
Yes, Wegovy can be effective for weight loss in eligible UK adults — but effectiveness varies between individuals. Clinical trials showed that semaglutide (the active ingredient in Wegovy) helped participants lose an average of 15% of their body weight over 68 weeks, alongside a reduced-calorie diet and increased physical activity. However, Wegovy is a prescription-only weekly weight loss injection that requires a clinical assessment before being prescribed. It's not suitable for everyone, and results depend on your individual health, lifestyle changes, and how your body responds to the medication.
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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 Effective Is Wegovy — Clinical Evidence
Wegovy (semaglutide) is a GLP-1 receptor agonist — a weekly weight loss injection licensed in the UK for adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. In the STEP-1 clinical trial, participants taking the maximum 2.4 mg dose lost an average of 14.9% of their body weight at 68 weeks — roughly 14 kg for a 95 kg adult — compared to 2.7% in the placebo group.
Effectiveness depends on: consistent weekly injections, a reduced-calorie diet (typically 500 kcal deficit), regular physical activity, and individual factors like metabolism and adherence. Some people lose more, some less — individual results vary significantly. Wegovy works by reducing appetite, increasing feelings of fullness, and slowing gastric emptying (how quickly food leaves the stomach).
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 vs Mounjaro — Which Is Better For Weight Loss?
Both Wegovy and Mounjaro are prescription-only weight loss injections available in the UK, but they work slightly differently. Wegovy is a GLP-1 agonist only, whereas Mounjaro is a dual GIP + GLP-1 agonist — meaning it activates two hormone pathways instead of one. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21% of body weight) compared to Wegovy (15%), but this doesn't mean Mounjaro is definitively "better" — individual responses vary, and some people respond better to one than the other.
Your prescriber will assess which medication suits you based on your health history, other medications, and individual circumstances. Neither is universally superior — choice depends on personalised clinical assessment. Try our GLP-1 weight loss calculator to explore potential outcomes at different doses 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 → 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.
How much weight will I lose on Wegovy?
Clinical trials showed an average of clinically studied weight loss at the maximum dose (2.4 mg weekly) over 68 weeks — but individual results vary significantly. Some people lose more, some less. Results depend on your starting weight, diet, exercise, metabolism, and adherence to treatment. Your prescriber can discuss realistic expectations based on your individual circumstances.
Is Wegovy available on the NHS in the UK?
Wegovy is not routinely available on the NHS for weight management — access is very limited and varies by region. Most people access Wegovy through private online prescribing following a clinical assessment with a UK-licensed prescriber. NHS access is sometimes available through tier 3 specialist weight management services, but waiting lists can be very long.
What is the difference between Wegovy and Mounjaro?
Wegovy contains semaglutide (GLP-1 agonist only), while Mounjaro contains tirzepatide (GIP + GLP-1 agonist). Both are weekly injections, but Mounjaro activates two hormone pathways. Wegovy starts at 0.25 mg and goes up to 2.4 mg; Mounjaro starts at 2.5 mg and goes up to 15 mg. Clinical trial data shows similar average weight loss, but individual responses differ.
What are the main side effects of Wegovy?
The most common side effects include nausea, diarrhoea, vomiting, and constipation — especially when starting or increasing doses. These usually improve over time. Other side effects can include headache, fatigue, and indigestion. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder problems — seek immediate medical attention if these occur.
How do I get Wegovy prescribed in the UK?
Wegovy is prescription-only and requires a clinical assessment. You can access it through a private online consultation with a UK-licensed prescriber, who will assess your eligibility based on BMI, health conditions, and medications. Your GP cannot prescribe Wegovy directly unless through a specialist NHS service. Use the BMI calculator on this page to check if you may be eligible for prescription weight loss treatment.
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.