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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Mounjaro Shot in Thigh: UK Self-Injection Guide
Injecting Mounjaro (tirzepatide) into your thigh is one of the three recommended self-injection sites available in the UK. The thigh offers a convenient, accessible area for your once-weekly dose, though you'll need to rotate injection sites to prevent lipohypertrophy (thickened tissue). This guide covers the safe technique, site rotation, and what the NHS and MHRA recommend for Mounjaro self-administration.
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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.
Mounjaro Thigh Injection: How to Inject Safely
The upper thigh (quadriceps area) is an approved injection site for Mounjaro and offers practical advantages for self-administration. Site rotation is essential — inject at least 1 cm away from previous injection marks to prevent tissue damage and ensure consistent medication absorption.
- Pinch the thigh: Gently pinch a fold of skin and fat on the outer or front of your thigh (roughly mid-thigh level)
- Insert the needle: Push the Mounjaro KwikPen needle straight in at a 90-degree angle through the pinched skin
- Inject slowly: Hold the pen in place for 3 seconds after pressing the injection button
- Remove and apply pressure: Pull the needle out straight, then apply light pressure with a clean tissue for a few seconds
The thigh has fewer nerve endings than other sites, making it less sensitive to injection discomfort. Always let your Mounjaro pen reach room temperature before injecting (minimum 30 minutes out of the fridge).
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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.
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Thigh Site Rotation and NHS Guidance
Rotate sites systematically — alternate between your left and right thigh, changing the exact injection point each week within the upper thigh region. Keep a simple log or use a progress tracker to record where you injected, ensuring you never use the same spot within at least four weeks.
The NHS and MHRA recommend three approved injection sites: stomach (abdomen), upper thigh, and upper arm (upper arm requires assistance). Thigh injection is particularly practical if you're self-administering and want to avoid the stomach area or need more privacy. If you notice any redness, bruising, swelling, or hardened tissue at injection sites, inform your prescriber — these signs may indicate lipohypertrophy or infection requiring attention.
- 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 it safe to inject Mounjaro into the same thigh every week?
No — you must rotate injection sites within the thigh area. Injecting in the same spot repeatedly risks lipohypertrophy (thickened, hardened tissue that reduces medication absorption). Alternate between your left and right thigh, and vary the exact injection point by at least 1 cm each week. Keep a simple log to track sites.
How do I know if my Mounjaro thigh injection went wrong?
After injection, you should see a small, temporary mark or bruise. Seek immediate advice if you notice severe pain, significant swelling, warmth, redness, or pus — these may indicate infection. Minor bruising is normal. If you missed the injection (no resistance felt), contact your prescriber or pharmacist for guidance.
Can I inject Mounjaro into my thigh if I'm overweight?
Yes — the thigh is suitable regardless of your weight. If you have difficulty pinching a skin fold on your thigh, try lying down or sitting with your leg relaxed. Your prescriber or nurse can demonstrate the technique if you're unsure. The key is injecting into skin and fat tissue, not muscle directly.
Does thigh injection hurt more than stomach or arm injection?
Pain varies by individual, but the thigh typically has fewer nerve endings than the stomach, making it potentially less uncomfortable. Stomach injection is often described as slightly more sensitive. Arm injection requires assistance. Try different sites to find what works best for you personally.
What should I do if I get a bruise after injecting into my thigh?
Minor bruising is normal and usually resolves within a few days. To minimise bruising: ensure your Mounjaro is at room temperature before injecting, avoid injecting over blood vessels or bruised areas, and apply gentle pressure (not rubbing) after removal. If bruising is severe or doesn't fade, contact your GP or prescriber.
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