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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Semaglutide Injections For Weight Loss In The UK
Semaglutide is a prescription-only GLP-1 receptor agonist injection licensed in the UK for weight management in adults. Marketed as Wegovy, this weekly injection is available through both NHS specialist services and private prescribing routes. Clinical trials showed that semaglutide can help adults lose an average of around 15% of their body weight, though results vary significantly between individuals. Alongside a reduced-calorie diet and increased physical activity, semaglutide addresses how the body regulates appetite and food intake. This guide explains NHS eligibility, how semaglutide works, and your options for access 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 Semaglutide Works And NHS Eligibility Criteria
How semaglutide works: Semaglutide is a GLP-1 receptor agonist — it activates the GLP-1 hormone pathway in the brain and gut. This may help reduce appetite and food cravings, support feeling fuller after smaller meals, and slow how quickly food leaves the stomach. Unlike insulin, it does not directly lower blood sugar, though it does support better blood glucose control in people with type 2 diabetes.
NHS eligibility for semaglutide (Wegovy): Adults with a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with at least one weight-related health condition, may be eligible. Weight-related conditions include type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or a history of heart attack or stroke. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds of 27.5 or above may apply, reflecting higher health risks in these populations at lower BMI levels.
- Age: 18 years or older
- Not pregnant or breastfeeding
- No allergy to semaglutide or ingredients
- No severe gastroparesis or digestion problems
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.
NHS Access Vs Private Route For Semaglutide In The UK
NHS route: Semaglutide is available through NHS tier 3 specialist weight management services following referral from your GP. NICE has approved semaglutide for use within NHS weight management pathways. However, availability varies significantly by region — some ICBs (integrated care boards) have access, others do not, and waiting lists can extend several months to over a year in many areas. Your GP can advise whether your local NHS services currently prescribe semaglutide.
Private route: Semaglutide is available through GPhC-registered online pharmacies following an online consultation with a UK-licensed prescriber. This route does not require NHS referral and typically offers faster access. Costs range from approximately £130–£250 per month depending on dose (0.25 mg to 2.4 mg weekly). Track your progress with our free progress tracker as you adjust to treatment.
Use our GLP-1 weight loss calculator to estimate potential weight loss outcomes at different semaglutide doses based on the STEP trial data. The calculator helps you understand realistic expectations — the STEP-1 trial showed average weight loss of approximately 14.9% body weight at 68 weeks on the 2.4 mg maintenance dose, alongside diet and activity changes. Our BMI calculator also helps you track whether your weight sits within a healthy range as you progress, and our weight converter lets you easily switch between kg, stone, and pounds as you monitor your journey.
- 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 semaglutide (Wegovy) and Ozempic?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes (doses up to 2 mg) while Wegovy is licensed specifically for weight management (doses up to 2.4 mg). Ozempic is not licensed for weight loss in the UK — using it off-label for weight loss is not recommended. Wegovy is the appropriate licensed option for weight management in the UK.
How long does semaglutide take to work for weight loss?
Weight loss typically becomes noticeable within 2–4 weeks, with more significant results visible over 8–12 weeks. The STEP trial measured results at 68 weeks on the full 2.4 mg dose. Most people stay on semaglutide as a long-term treatment — weight loss plateaus if the injection is stopped, so consistency is important for sustained results.
Can I get semaglutide injections on the NHS in my area?
Semaglutide access through the NHS varies significantly by region. Your GP can check whether your local tier 3 specialist weight management service currently prescribes semaglutide. If your area does not offer NHS access, private online prescribing is an alternative route. Contact your GP or local integrated care board for current availability.
What are the most common side effects of semaglutide injections?
The most common side effects include nausea, diarrhoea, constipation, and stomach pain — particularly in the first 4–8 weeks. These typically ease as your body adjusts. Serious side effects are rare but include severe stomach pain (possible pancreatitis), gallbladder problems, and serious allergic reactions. Always inform your prescriber of any concerning symptoms.
How much weight can I expect to lose with semaglutide?
Clinical trial data showed average weight loss of approximately 14.9% of body weight at 2.4 mg weekly over 68 weeks. However, individual results vary significantly — some people lose more, others less. Weight loss depends on your starting weight, adherence to diet and activity changes, genetics, and how your body responds to the medication. Our weight loss calculator can provide a personalised estimate based on trial averages.
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.