Mounjaro Injection Sites: Where to Inject Mounjaro?

Mounjaro is one of several popular weight loss injections available in the UK. Its active ingredient (tirzepatide) works by dramatically lowering appetite and calorie consumption. This can lead to significant weight loss, with some studies reporting weight reductions of up to 22.4% over 72 weeks of treatment.

Mounjaro is administered on a weekly basis via subcutaneous injection. This puts it on par with weight loss treatments like Wegovy; however, it differs from Nevolat, which is injected once per day. Having a clear understanding of and being comfortable with how to administer your medication is a crucial part of any treatment plan, so it’s important to be prepared.

Fortunately, learning how and where to inject Mounjaro is relatively straightforward. Here, we’ll discuss Mounjaro injection sites, potential reactions and side effects, and how to administer your treatment safely.

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Where to Inject Mounjaro 

Mounjaro is a subcutaneous injection, meaning it’s injected into the fatty tissue just under the skin. The best places to inject Mounjaro are your stomach, upper arms, or upper thighs. These body parts have plenty of fatty tissue to accommodate the needle and allow for effective absorption of the medication.

The first thing to consider when choosing between the different Mounjaro injection sites is who will administer the medication. If you plan to inject yourself, the stomach and upper thighs are the easiest body parts to reach. If you want the injection in your upper arm, you may need someone else to help you.

If you choose to inject into your abdomen, pick a site at least 5 cm from your belly button. You can inject Mounjaro into the same body part every week, but you should pick an injection site at least 2.5 cm from the previous week’s dose. For example, you could inject into alternating sides of your stomach each week. This will reduce the risk of skin reactions and help your body to absorb the medication effectively.

Your injection site should be healthy and free from existing injuries. This means no redness, swelling, scarring, or bruising. If you also inject insulin, choose a different injection site for your Mounjaro dose.

Where is the Best Place to Inject Mounjaro for Maximum Weight Loss?

There is currently no evidence to suggest that any of the recommended injection sites are superior to the others in terms of weight loss. Clinical studies indicate there is no difference in the effects of tirzepatide injected into the thigh, arm, or stomach. Therefore, you will get the same benefits no matter which of the Mounjaro injection sites you choose.

How to Choose Your Mounjaro Injection Site

Although Mounjaro works the same regardless of where you take it, there are certain things to consider when deciding which area you want to use. These include how easy it is to access the Mounjaro injection site and how comfortable administering the dose is.

The first question to answer is who will administer your Mounjaro. If you plan to inject yourself, you can probably rule out the upper arm as an injection site. This spot is difficult to reach unless you have someone else to help you, and comfort and ease of access are two key factors for a safe and effective injection. That being said, the upper arm may be a suitable alternative if you prefer to inject in a less visible area.

If you’re administering the injection yourself, the stomach is typically the easiest place to reach. It also has a large surface area and is a significant source of subcutaneous fat, allowing you to rotate your injection site each week. If you want to inject Mounjaro into your abdomen, remember to choose a site at least 5 cm from your belly button. This is because there is tough connective tissue around this area, which may make Mounjaro absorption difficult.

The upper thigh is also a convenient place to inject as, like the stomach, it’s easy to reach, has a large surface area, and is a good source of subcutaneous fat. If you’re injecting into your thigh, choose a site on the front of the leg and avoid injecting into your inner thigh. 

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Mounjaro Injection Sites: Reactions and Side Effects

Injection site reactions are a common side effect of Mounjaro, affecting up to 10% of users. Symptoms of injection site reactions include redness, a rash, itching, or swelling of the skin where you administered Mounjaro. Doctors believe these reactions occur at a similar rate for patients using other GLP-1 medications, such as semaglutide (Wegovy).

Much more rarely, Mounjaro can trigger a severe allergic reaction. This may lead to swelling of the lips, tongue, and throat, as well as breathing problems, difficulty swallowing, and a rapid heart rate. Allergic reactions should be treated as a medical emergency. If you experience any of these symptoms, contact a clinician immediately.

How to Administer Mounjaro Safely

Learning how to administer Mounjaro correctly is key for anyone hoping to benefit from weight loss injections. The primary safety tips for injecting Mounjaro are to find a comfortable position, inspect the pen for damage, clean your hands and the injection site, prime the pen, and rotate the injection site weekly.

Find a Comfortable Position

Ensure you can maintain a comfortable position throughout the duration of your injection. Many people choose to inject into their abdomen or upper thigh because these body parts are typically easiest to reach.

Inspect your Mounjaro Pen

Do not use a Mounjaro pen that is visibly damaged or expired. You should also discard Mounjaro that appears cloudy, discoloured, contains particles, or has been frozen.

Clean Your Hands and Injection Site

Wash your hands with soap and water, and clean the injection site with an alcohol wipe before administering your injection. This will reduce your risk of infection from germs on the skin.

Prime the Pen

Priming your Mounjaro pen ensures it is working and removes air bubbles from the cartridge. It also confirms that medicine is flowing through the needle correctly. You only need to do this for the first injection from a new pen, and there is no need to prime a Mounjaro pen that is already in use.

Rotate the Injection Site Each Week

You can inject into the same body part each week, but you should rotate injection sites to reduce your risk of injection site reactions. If you take insulin, don’t inject this in the same place you inject Mounjaro.

If you'd like to know more about how to use the Mounjaro injection pen, please refer to our dedicated article or watch the video below.

Mounjaro Injection Sites: Frequently Asked Questions

Learning how to inject Mounjaro safely is key for anyone intending to start a treatment plan. Even those familiar with the injection process may still have questions regarding the best time of day to inject Mounjaro, whether they should change their injection site, and what to do about injection site reactions.

We’ll explore the answers to these questions and more below.

Should You Change Injection Sites for Mounjaro?

You should rotate your Mounjaro injection site weekly to reduce your risk of skin reactions. You can use the same body part each week, but you must inject into a different location. For example, you may alternate between the left and right sides of the stomach for each injection.

When is the Best Time to Inject Mounjaro?

There is no ‘best’ time of day to inject Mounjaro, as there is no known benefit to administering it in the morning, afternoon, or evening. You must inject Mounjaro on the same day, but you can pick the time most convenient for you. Consistency is crucial, so once you’ve established your dosing schedule, it’s essential to stick to it.

Mounjaro

Rated 0 out of 5 based on 0 reviews

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• Approved Weight Loss Treatment
• Suitable for adults with a BMI of +30kg/m²
• Pre-filled injection pen

• Discreet delivery next working day
• Online prescription - No doctor visit

Prices from £159.99 Review More Prices

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What Happens if You Inject Mounjaro in the Wrong Place?

If you administer Mounjaro at the same injection site as the week before, or within 5 cm of your belly button, you may experience a skin reaction. Monitor the site for signs of redness, swelling, itching, or bruising. If you are concerned, discuss your symptoms with a licensed clinician.

Should I Pinch My Skin When Injecting Mounjaro?

You don’t need to squeeze or pinch your skin when injecting Mounjaro. This is common practice for injecting insulin, as it ensures the needle goes into the fat layer under the skin. However, Mounjaro pens have a short needle and are used on body parts with plenty of subcutaneous fat (like the thigh or stomach), so pinching isn’t typically necessary.

Why is My Mounjaro Injection Site Swollen and Itchy?

Swelling or itching around your Mounjaro injection site may indicate a reaction. This is a relatively common side effect of Mounjaro, but it usually resolves on its own after a few days. In the meantime, you can relieve discomfort by applying cold compresses to the affected area.

If your symptoms persist after a few days, consult a clinician for further advice.

Support Throughout Your Weight Loss Journey

If you’re considering trying Mounjaro or any other weight loss treatment, it’s comforting to know that you have the support of a specialist team who can help you throughout your journey. This is exactly what Prescription Doctor provides.

Since 2013, we’ve helped countless individuals just like you to reach their goals, and we’re ready to do the same for you. Not only do we offer a wide range of different medications, but we’re also on hand to provide expert guidance on an array of subject areas. These range from advice on Mounjaro injection sites and potential exercise routines to tips for success, as well as help with diet plans and details about how weight loss injections actually work.

Our service doesn’t just stop at the point of purchase, either, as our clinicians will regularly check in with you to monitor progress and answer your queries whenever needed. A holistic approach to healthcare that you can rely upon.

Ready to get started? Fill out the online medical questionnaire and our clinicians will assess whether Mounjaro is suitable for you. Provided your order is approved before 3pm Monday to Friday, your order will be dispatched for next-day delivery in discreet packaging. Kickstart your Mounjaro journey with Prescription Doctor today. 

Authored By

Kate Latham

Medical Content Writer

Kate has been a scientific content writer since 2017. With a BSc in Biology and a background in cancer research, she is adept at identifying the latest findings in medical research and utilising these

Published on: 07/08/2025

Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist

Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Reviewed on: 07/08/2025