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 the Wegovy Jab?
The Wegovy jab is a prescription-only, once-weekly injection containing semaglutide, a GLP-1 receptor agonist approved in the UK for weight management in adults. It works by helping to reduce appetite and increase feelings of fullness after meals. Wegovy is not the same as Ozempic (which is also semaglutide but licensed for type 2 diabetes, not weight loss). Clinical trials showed that people using Wegovy alongside a reduced-calorie diet and increased physical activity lost an average of around 15% of their body weight — though individual results vary significantly. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses.
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 Wegovy Works and Eligibility
Semaglutide, the active ingredient in Wegovy, is a GLP-1 receptor agonist that mimics a natural hormone produced in the gut. It works by:
- Signalling to your brain that you feel full, reducing appetite and cravings
- Slowing how quickly food leaves your stomach
- Supporting better blood sugar control
- Helping you feel satisfied with smaller meals
In the UK, you may be eligible for Wegovy 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, high blood pressure, or sleep apnoea). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS applies lower BMI thresholds due to increased health risks at lower weights. Use our free BMI calculator to check your personal BMI instantly. Wegovy is prescription-only and requires assessment by a licensed prescriber to confirm suitability.
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 Doses, Side Effects, and Access in the UK
Wegovy doses start at 0.25 mg and escalate to a maximum of 2.4 mg, given once weekly. Each dose increase is typically separated by 4 weeks. Common side effects include nausea, diarrhoea, constipation, and stomach pain — these often improve as your body adjusts. Serious side effects are rare but may include severe stomach pain (possible pancreatitis) or gallbladder problems; seek urgent medical attention if these occur.
In the UK, you can access Wegovy via NHS specialist tier 3 weight management services (through your GP) or privately through licensed online prescribing services. NHS availability varies significantly by region. Private prescribing is faster but involves a cost. A prescriber will assess your individual health, medications, and medical history before issuing a prescription. Weight loss injections work best alongside lifestyle changes — diet, physical activity, and behaviour support.
- 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?
No. Both contain semaglutide, but Ozempic is licensed for type 2 diabetes management (doses up to 2 mg) and not approved for weight loss in the UK. Wegovy is the licensed weight management version with doses up to 2.4 mg. Using Ozempic for weight loss would be off-label.
How much weight will I lose on Wegovy?
Clinical trials showed an average weight loss of around 15% of body weight over 68 weeks on the maximum 2.4 mg dose. Individual results vary significantly and depend on dose, adherence, diet, and physical activity. Your prescriber can discuss realistic expectations for you.
Can I get Wegovy on the NHS in the UK?
Yes, through NHS tier 3 specialist weight management services. You'll need a GP referral. Availability and waiting times vary by region and ICB. Private prescribing is also available if you prefer faster access, though this involves a cost.
What are the most common Wegovy side effects?
Nausea, diarrhoea, constipation, and stomach pain are very common, especially when starting or increasing doses. These often settle within a few weeks. Most people find side effects manageable. Serious side effects are rare. Always discuss concerns with your prescriber.
How is Wegovy different from Mounjaro?
Wegovy (semaglutide) is a GLP-1 agonist — it activates one hormone pathway. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist — it activates two pathways. Clinical trials suggest Mounjaro may produce slightly more weight loss on average, though both are effective. Choice depends on individual suitability and prescriber guidance.
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.