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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Is Semaglutide Safe — Understanding Wegovy Safety in the UK
Yes, semaglutide is safe when prescribed and used correctly by UK adults who meet eligibility criteria. Semaglutide (brand name Wegovy) is a GLP-1 receptor agonist licensed by the MHRA for weight management. Like all medications, it carries potential side effects — mainly nausea and digestive changes — but serious adverse events are rare in clinical trials. Safety depends on proper medical assessment, correct dosing, and monitoring. This guide covers what semaglutide is, real costs in the UK, how to access it safely through NHS or private routes, and what safety monitoring involves.
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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.
Semaglutide Cost in the UK — NHS vs Private Routes
NHS Access: Semaglutide (as Wegovy) is available through NHS specialist weight management services, but access varies significantly by region. Most areas have lengthy waiting lists — sometimes 12–18 months or longer. When prescribed via NHS, the medication is provided at no cost to eligible patients. Referral to tier 3 specialist services is required; your GP cannot prescribe it directly.
Private Cost (approximate): Through private online prescribing services, semaglutide typically costs £129–£250 per month depending on dose. Starter doses (0.25–0.5 mg) cost less than maintenance doses (1.7–2.4 mg). You pay for the full course upfront; some services offer bulk discounts for 3–6 month plans. The cost per dose is roughly £30–£60 depending on the service and dose strength.
What affects cost: Dose, prescription frequency, dispensing pharmacy fees, and whether you need additional support or follow-up consultations. Always compare services — costs vary significantly across UK private providers.
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.
How to Access Semaglutide Safely — NHS and Private Routes
NHS Route: Ask your GP for a referral to your local specialist weight management service (tier 3). You'll be assessed for eligibility (BMI ≥30, or ≥27 with weight-related conditions). If approved, semaglutide may be offered alongside lifestyle support. Expect to wait weeks or months. Once dispensed, you'll receive injection training and regular follow-up appointments at no cost.
Private Route: Register with a UK-registered online prescribing service. Complete a medical questionnaire and online consultation. A UK-licensed prescriber will assess whether semaglutide is safe and appropriate for you. If approved, your prescription is sent to a GPhC-regulated pharmacy for dispensing. The entire process typically takes 24–48 hours. You'll receive self-injection guidance and can order subsequent doses online.
Safety first: Never obtain semaglutide without a valid UK prescription or from unlicensed sources — counterfeit versions exist and pose serious health risks.
- 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 semaglutide safe for everyone?
No. Semaglutide is not safe for people under 18, those who are pregnant or breastfeeding, anyone with a history of medullary thyroid cancer, or those allergic to semaglutide. It requires careful assessment by a prescriber. Existing medical conditions — particularly pancreatitis, gallbladder disease, or severe kidney problems — may require dose adjustment or make it unsuitable.
What are the most common side effects of semaglutide?
Nausea, vomiting, diarrhoea, and constipation are very common, especially when starting or increasing doses. These usually ease after 4–8 weeks as your body adjusts. Most people find side effects manageable with slower dose increases and dietary adjustments. Serious side effects are rare in clinical trials.
Can I get semaglutide on the NHS quickly?
Not usually. Most NHS areas have waiting lists of 6–18 months or longer for specialist weight management services where semaglutide is prescribed. Private prescription routes are much faster — typically 24–48 hours from consultation to dispensing — though you pay the full cost yourself.
Is it safe to buy semaglutide online?
Only from registered UK services that require a valid prescription from a UK-licensed prescriber. Always check that the service is GPhC-regulated and the prescriber is on the medical register. Never buy from unregulated overseas sources or services that don't require proper assessment — counterfeit and substandard products are common online.
Will my GP monitor me if I get semaglutide privately?
Your GP should be informed you're using semaglutide and can provide monitoring support — blood pressure, weight checks, and diabetes screening if relevant. Some private prescribing services offer their own follow-up consultations. Always inform your GP of any medications you're taking, including semaglutide.
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.