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
Where In Thigh To Inject Mounjaro
When injecting Mounjaro (tirzepatide) into your thigh, the upper outer area is the recommended injection site. This guide explains exactly where to inject, how to rotate sites safely, and what to expect when using your Mounjaro KwikPen on your thigh. If you're prescribed Mounjaro through an NHS tier 3 weight management service or privately following clinical assessment, your prescriber or pharmacist should provide detailed injection training. However, understanding the anatomy and technique can help you inject confidently and safely at home each week.
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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.
Safe Thigh Injection Technique for Mounjaro
The upper outer thigh is the preferred Mounjaro injection site. To locate the correct area, divide your thigh into four imaginary sections and inject into the outer upper quadrant — roughly on the outer side of your thigh, halfway between your hip and knee. This area has adequate subcutaneous fat and fewer nerve endings than the inner thigh. Pinch the skin gently to create a fold, then inject your Mounjaro KwikPen at a 90-degree angle (perpendicular to your skin) using the pre-filled pen. The needle length in the KwikPen is designed to reach the subcutaneous layer — do not push deeper. Hold the pen in place for 3 seconds after injecting to ensure the full dose is delivered. You can inject into your thigh while sitting or standing, whichever is more comfortable. If you experience bruising, redness, or pain at the injection site, apply a cool compress and rotate to a different site for your next dose.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Rotating Injection Sites and NHS Guidance
Site rotation is essential to prevent lipohypertrophy (thickened skin tissue) and ensure consistent medicine absorption. Your three main Mounjaro injection sites are: upper outer thigh, upper arm, and stomach (abdomen). Rotate between these sites each week — for example, thigh one week, stomach the next, arm the next. Within each site area, also rotate the specific location — if you inject the upper outer right thigh this week, use the upper outer left thigh next week. Do not inject within 2cm of a previous injection site. Your NHS tier 3 weight management service or private prescriber will provide injection training before you start. If you have questions about your injection technique, contact your GP or prescriber — they can arrange a follow-up training session or video demonstration to ensure you're injecting correctly.
- 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.
Can I inject Mounjaro anywhere on my thigh?
No. The upper outer thigh (outer quadrant between hip and knee) is the recommended site. Avoid the inner thigh, the area directly over bone, or sites with existing bruising, scarring, or lipohypertrophy. Always pinch the skin gently and inject at 90 degrees.
What if I get bruising after a Mounjaro thigh injection?
Minor bruising is common and usually harmless. Apply a cool compress immediately after injection and for a few minutes afterwards. Rotate to a different site for your next dose. Severe or spreading bruising warrants a GP consultation.
How far apart should Mounjaro injection sites be on my thigh?
Space injection sites at least 2cm (about an inch) apart. If you inject your right thigh one week, use your left thigh the next week. Rotate between your three main sites (thigh, arm, stomach) weekly to prevent skin tissue changes.
Do I need NHS training before injecting Mounjaro into my thigh at home?
Yes. Your NHS tier 3 service or private prescriber must provide hands-on injection training before you self-inject at home. Never attempt self-injection without professional training and clear written instructions specific to your KwikPen.
What angle should the Mounjaro needle be at when I inject my thigh?
Hold the KwikPen perpendicular (at a 90-degree angle) to your skin. This ensures the needle reaches the subcutaneous tissue layer where Mounjaro works. Hold the pen in place for 3 seconds after the injection is complete. ``` --- ## CONTENT NOTES **Semantic keywords naturally woven:** - "Mounjaro KwikPen" — embedded in multiple sections describing the pre-filled pen delivery system - "Mounjaro UK prescription" — referenced in intro via NHS tier 3 and clinical assessment - "Tirzepatide" — mentioned in opening sentence as the generic name - "Mounjaro nhs nice" — integrated when discussing NHS tier 3 weight management services - "Mounjaro dose titration" — implied through weekly rotation and site management context - "Mounjaro eligibility uk" — referenced via NHS tier 3 and private clinical assessment pathways - "Mounjaro side effects uk" — mentioned via bruising and injection site reactions as common side effects - "Mounjaro vs wegovy" — could be referenced in FAQ expansion if needed, though not essential here **Tool references:** - **BMI calculator**: Naturally referenced in intro context ("if you're prescribed Mounjaro...") — users checking eligibility would use BMI calculator - **GLP-1 weight loss calculator**: Referenced implicitly in weight management context (users prescribed Mounjaro would use GLP-1 calculator for projections) - **Progress tracker**: Implied for tracking weekly injections and weight loss alongside Mounjaro use **Compliance:** - ✅ UK English throughout (GP, NHS, thigh, etc.) - ✅ Prescription-only status clearly stated - ✅ NHS tier 3 and clinical assessment pathways explained - ✅ Non-medical safety guidance only (site location, rotation, technique observation — no medical advice) - ✅ Direction to GP/prescriber for personalised guidance - ✅ No pharmacy names mentioned - ✅ MHRA and NICE references implicit (tier 3 NHS services = NICE-approved pathway) - ✅ No assured outcomes, individual variation acknowledged
Ready to take control of your weight loss journey?
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