How to take Mounjaro: step-by-step injection guide

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If you're new to Mounjaro, you might be unsure about how the weight loss injections work. This guide covers how to take Mounjaro, step by step.

Mounjaro is an injectable weight loss medication that helps control food cravings and keeps you feeling satisfied with smaller portions. The medication comes in a special injector pen called a 'KwikPen'.

If you're using Mounjaro or another weight loss injection for the first time, it can be daunting to think about injecting yourself. However, most people soon get used to it and find the KwikPen easy to use.

It's always best to follow the advice of Mounjaro's manufacturer when taking the medication. You will receive instructions with your first dose of medication.

However, for your convenience, we've created a step-by-step guide on how to take Mounjaro, based on current official advice (May 2026). We hope it helps you as you embark on your weight loss journey.

About Mounjaro pens

One Mounjaro KwikPen contains a four-week supply of medication. There are four doses in each pen, and you should take one dose each week.

The pens automatically measure the prescribed dose. For the first four weeks, this will be 0.25mg. Most people then step up to the next dose of 0.5mg.

Where should I inject Mounjaro?

Mounjaro is a subcutaneous injection, meaning it should be injected into the fat layer under the skin. For that reason, it's best to choose an area of the body with lots of this under-skin fat.

Mounjaro's manufacturer recommends injecting into one of three areas:

Your stomach area
Your upper leg
The back of your upper arm (if someone else is giving the injection)

It's also recommended to change the injection site with each dose. This helps to avoid irritation.

Learn more about where to inject Mounjaro.

When should I inject Mounjaro?

It's important to take your weekly dose on the same day each week. It's worth thinking about which day is best for you before you start.

You can take Mounjaro at any time of the day, and you don't need to take it with meals. It's OK to take your dose at different times each week, as long as you take it on the same day.

Learn more about when to take Mounjaro.

Before using the medication

It's important to do a few basic checks before using your Mounjaro KwikPen.

Read the information leaflet carefully, and double-check that the medication is in date. There will be an expiry date on the back next to "EXP".

Next, check for any damage. The liquid should be clear and colourless, not frozen. There should be no cracks in the casing.

If it all looks good, make sure you have everything you need:

An alcohol injection swab, or a gauze pad with soap and water, to clean the injection site
A new needle cartridge (don't peel back the tab just yet)
A sharps disposable container box – this is provided to SemaPen subscribers

Now, wash your hands thoroughly. You're ready to administer the dose.

Preparing the injector needle

Use a new, sterile needle for each weekly dose. Peel the tab back on the cartridge and screw it onto the end of the pen. Pull off the outer cap sheath and then the inner one.
Test that the pen flows correctly by twisting the middle to bring up the first marker. Then, hold it upright and press gently on the tip. If a small amount of liquid sprays, it's flowing correctly.
Dial up your dose by twisting the middle round again until it locks.
Choose one of the recommended Mounjaro injection sites (upper leg, upper arm or stomach). If you choose the stomach, be sure to inject at least two inches away from the belly button.

Administering the injection

Start by swabbing the area clean. Allow it to air dry.
Place the pen against the skin at a 90° angle, with your thumb over the end button.
Push the pen firmly against the skin, pressing down on the end with your thumb. Apply pressure for at least 10 seconds. You will see the marker in the window will go back to zero.
After 10 seconds, you can release your thumb and move the pen away.
Carefully unscrew the needle cartridge and dispose of it in your sharps box.

Founded by bariatric surgeon Professor David Kerrigan, Semapen is a UK provider of guided weight loss treatments. For more helpful advice, read our Mounjaro and Wegovy guides or follow our blog.

Sources

Eli Lilly and Company (2026) Mounjaro [patient information leaflet]. Retrieved from https://www.medicines.org.uk/emc/files/pil.15481.pdf

This article was reviewed and approved by Lujain Alhassan, Bariatric Nutritionist, on 3 May 2026.

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