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
How To Take Wegovy — Step-by-Step UK Guide
Wegovy (semaglutide) is a prescription-only, once-weekly injection for weight management available in the UK. This guide explains exactly how to take it safely and effectively — from your first injection through to maintenance doses. Wegovy works as a GLP-1 receptor agonist, helping regulate appetite and support sustainable weight loss alongside diet and physical activity. You'll need a prescription following a clinical assessment from a UK-licensed prescriber before you can access Wegovy.
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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.
Wegovy Dosing Schedule and Injection Technique
Wegovy comes as a pre-filled auto-injection pen, and you inject yourself once per week on the same day each week. The dosing schedule gradually increases over 16–20 weeks:
- Weeks 1–4: 0.25 mg (starting dose)
- Weeks 5–8: 0.5 mg
- Weeks 9–12: 1 mg
- Weeks 13–16: 1.7 mg
- Week 17 onwards: 2.4 mg (maximum maintenance dose)
Each pen contains four doses, lasting four weeks. Your prescriber will guide you through the escalation schedule. You must wait at least four weeks at each dose before increasing — do not skip ahead. Most people reach the 2.4 mg maintenance dose after approximately five months of treatment. This gradual approach helps your body adapt and reduces nausea and other side effects common with GLP-1 injections. Always follow your prescriber's specific instructions for your individual escalation plan.
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.
Injection Technique and Storage
Choose one of three injection sites: your stomach (abdomen), upper thigh, or upper arm — rotate sites each week to avoid irritation. The auto-injection pen does the work for you: remove the pen from the fridge, let it reach room temperature for 15 minutes, remove the needle cap, press the pen firmly against your skin at a 90-degree angle, and press the button to inject. Storage is critical: keep unopened pens in a fridge at 2–8°C in their original carton. After first use, you can store the pen at room temperature (below 30°C) for up to 30 days, then dispose of it. Never freeze Wegovy — if frozen, it cannot be used. Always check the expiry date before injecting.
- 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 if I miss a Wegovy injection?
If you miss a dose within 4 days, inject as soon as you remember, then continue your normal schedule the following week. If more than 4 days have passed, skip that dose and inject on your normal scheduled day. Never inject two doses close together. Minimum time between doses is 3 days.
Can I switch between injection sites?
Yes, rotating sites is recommended. You can inject into your stomach, upper thigh, or upper arm (though arms need assistance). Rotating weekly reduces irritation and bruising at any single site. Your prescriber may provide specific guidance.
Does Wegovy work better than Mounjaro?
Both are licensed GLP-1 medications in the UK. Wegovy contains semaglutide; Mounjaro is a dual GIP/GLP-1 agonist. Clinical trials show similar average weight loss (around 15% body weight), though individual results vary significantly. Your GP or prescriber can advise which suits your health situation best.
What happens if I inject Wegovy incorrectly?
The auto-injection pen is designed to be straightforward and difficult to use incorrectly. If you're unsure, your prescriber or pharmacist can demonstrate the technique, and many offer online video guidance. If you have concerns after injecting, contact your prescriber or NHS 111 for advice.
Can I adjust my Wegovy dose myself?
No — only your prescriber can change your dose. Do not skip doses or increase faster than prescribed, as this increases side effect risk. If you're not tolerating your current dose, contact your prescriber to discuss options. Some people pause at lower doses if nausea is significant.
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.