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
Does Wegovy Work for Weight Loss?
Yes, clinical evidence shows that Wegovy (semaglutide) can help with weight loss in UK adults. In trials, people taking Wegovy lost an average of around 15% of their body weight over 68 weeks when combined with diet and exercise. However, results vary between individuals, and Wegovy is a prescription-only medicine requiring a clinical assessment. Weight loss isn't assured, but for many people, this GLP-1 receptor agonist injection provides meaningful support alongside lifestyle changes. Our GLP-1 weight loss calculator can help you explore potential outcomes.
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.
How Does Wegovy Work?
Wegovy contains semaglutide, a GLP-1 receptor agonist that mimics a natural gut hormone called glucagon-like peptide-1. When you take a weekly injection, it helps your body feel fuller after smaller meals, reduces cravings, and slows how quickly food leaves your stomach. This triple mechanism means you naturally eat less without feeling deprived.
- Signals fullness to your brain
- Reduces appetite and food cravings
- Slows stomach emptying
- Available as a once-weekly injection
Wegovy works best when combined with a reduced-calorie diet and increased physical activity. The injections come in five escalating doses (0.25 mg up to 2.4 mg), so your prescriber can find the right dose for you. Unlike older weight loss approaches, Wegovy addresses the hormonal side of weight management.
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.
What Results Can You Expect?
Based on the STEP-1 clinical trial, people taking Wegovy (2.4 mg) lost an average of 14.9% of their body weight—roughly equivalent to someone weighing 100 kg losing around 15 kg (2 stone 5 lbs). However, individual results vary significantly; some people lose more, some less. Results depend on your starting weight, diet adherence, exercise level, and how your body responds to semaglutide.
Most weight loss occurs during the first 6–12 months. Try our free BMI calculator above to see your current status and healthy weight range, then track progress with our progress tracker as you go.
- 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 long does it take for Wegovy to work?
Most people notice reduced appetite within the first 2–4 weeks of starting Wegovy. Measurable weight loss typically becomes visible after 4–8 weeks. However, maximum benefit takes time—clinical trials ran for 68 weeks to show full results. Your prescriber will adjust your dose gradually over 16 weeks to reach the effective maintenance dose of 2.4 mg.
Is Wegovy the same as Ozempic?
Both Wegovy and Ozempic contain semaglutide, but they're different medicines. Ozempic is licensed for type 2 diabetes (doses up to 2 mg) and using it for weight loss is off-label. Wegovy is the licensed UK weight management version at doses up to 2.4 mg. Always use the medication prescribed for your specific condition.
How does Wegovy compare to Mounjaro?
Wegovy (semaglutide) is a single GLP-1 agonist. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, which may explain slightly higher average weight loss in trials (~20.9% vs ~15%). Both require prescriptions, both are once-weekly injections, and both work best with diet and exercise. Individual response varies—your prescriber can help choose what's suitable for you.
Who can get Wegovy on the NHS?
NHS prescribing of Wegovy varies significantly by region. Access is typically through tier 3 specialist weight management services—you'd need referral from your GP. Waiting lists can be long. Private prescription through a UK-licensed prescriber is an alternative if you meet clinical eligibility (BMI ≥30, or ≥27 with weight-related health conditions like type 2 diabetes or hypertension).
What are the main side effects of Wegovy?
Very common side effects include nausea, diarrhoea, constipation, vomiting, and stomach pain—especially when starting or increasing doses. Most side effects settle over time. Serious side effects are rare but include severe stomach pain (possible pancreatitis), gallbladder problems, and serious allergic reactions. Always report unusual symptoms to your prescriber promptly.
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.