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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How to Safely Inject Mounjaro in Your Thigh
Yes, the thigh is one of the three recommended injection sites for Mounjaro (tirzepatide). Many people find it convenient for self-injection since it's easy to access and rotate between left and right thigh. This guide explains the correct technique, preparation, and what to expect when injecting Mounjaro in your thigh as part of your prescription weight management treatment in the UK.
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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 — Step-by-Step Technique
The upper thigh (front and outer side) is an ideal injection site for Mounjaro. To inject safely: clean the skin with an alcohol wipe and let it dry for at least 30 seconds. Pinch a fold of skin between your thumb and fingers. Hold the KwikPen perpendicular to the skin (90-degree angle) and push the needle straight in. Press the injection button and hold it down for 3 seconds to ensure the full dose is delivered. Remove the pen slowly and release the skin fold. Apply gentle pressure with a clean tissue if needed.
- Always use a fresh needle — never reuse a needle from a previous injection
- Rotate between left and right thigh each week to prevent lipohypertrophy (thickened tissue at injection sites)
- Inject at least 2–3cm away from previous injection sites
- Never inject into areas that are bruised, hardened, scarred, or numb
- Allow the KwikPen to reach room temperature before injecting (approximately 15–30 minutes after removing from 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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Site Rotation & Common Questions About Thigh Injections
Rotating your injection sites is essential to prevent complications and ensure consistent medication absorption. You have three approved Mounjaro injection sites: stomach (abdomen), upper thigh, and upper arm — though the upper arm requires assistance. Many people use the thigh and stomach alternately on a weekly schedule. If you experience pain, bruising, itching, or redness at an injection site, wait until symptoms resolve before injecting in that area again. Use our GLP-1 weight loss calculator to track your progress while taking Mounjaro, and remember that consistent injection technique combined with dietary changes and increased physical activity supports the best outcomes. Always contact your prescriber if you have concerns about injection technique or site reactions.
- 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 directly into muscle in my thigh?
No. Mounjaro is designed for subcutaneous injection — into the layer of fatty tissue beneath the skin, not into muscle. Injecting into muscle can cause pain and affect how the medication works. The outer and front areas of the thigh have sufficient subcutaneous tissue for safe injection.
How far should I space Mounjaro injections apart on my thigh?
Space each injection at least 2–3cm (approximately one finger width) away from the previous injection site. This prevents tissue damage and lipohypertrophy. Rotating between your left and right thigh each week helps spread injection sites across a larger area.
What should I do if I get a bruise or lump at my thigh injection site?
Minor bruising is common and usually resolves within a few days. Avoid injecting in that area until the bruise fades. Lumps or hardened areas (lipohypertrophy) can develop with repeated injections in the same spot — this is why rotation is important. If lumps persist or become painful, contact your GP or prescriber.
Is thigh injection more painful than stomach injection?
Pain tolerance varies between individuals. Some people find thigh injection less comfortable than stomach injection because the thigh has fewer nerve endings but more muscle tissue underneath. If thigh injection causes significant pain, discuss alternative sites with your prescriber. Many people alternate between sites based on comfort.
Do I need to pinch my thigh skin when injecting Mounjaro?
Yes, pinching a fold of skin is recommended for thigh injections to ensure you're injecting into the subcutaneous layer rather than hitting muscle beneath. This is especially important on the thigh because the fatty layer can be thinner than on the stomach. Use your thumb and fingers to create a gentle fold before inserting the needle.
Ready to take control of your weight loss journey?
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