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Home / Weight Loss / Mounjaro injection pen / How to inject Mounjaro

How to inject Mounjaro

A doctor’s step-by-step guide

If you’re about to take your first Mounjaro injection, it’s completely normal to feel a little unsure about how it works.

In this guide, I’ll walk you through the steps so you can feel confident giving your injection safely and comfortably.

Before you inject

Before taking your dose, there are a few simple things you should do to prepare.

First, wash your hands thoroughly with soap and water.

Next, check the injection pen. Make sure:

It’s important to take a moment to double-check your dose before each injection, as this can change over time as you move through your treatment plan.

If your pen has been stored in the refrigerator, allow it to reach room temperature for around 30 minutes before use to make the injection more comfortable.

Avoid heating the pen or placing it in hot water. If the medicine is frozen or cloudy, do not use it.

Storage reminder

Store Mounjaro in the refrigerator (2–8°C). Do not freeze it. If you need to carry it with you, it can be kept at room temperature (below 30°C) for up to 30 days, but avoid leaving it in a hot car or in direct sunlight.

Where to inject

Mounjaro is injected under the skin (subcutaneously).

The recommended injection areas are:

  • the stomach (abdomen)
  • the front of the thigh
  • the upper arm

Most people find the stomach or thigh the easiest places to inject.

Try to avoid injecting into the exact same spot each week. Rotating your injection site can help reduce irritation or soreness.

Here I’ve illustrated the recommended Mounjaro injection sites.

Diagram showing recommended Mounjaro injection sites on the abdomen, front of the thigh, and upper arm

Do not inject into skin that is:

  • bruised
  • scarred
  • tender
  • irritated

Priming your pen

Each pen needs to be primed before it can be used for the first time. Follow these instructions before your first injection:

  1. Attach a needle to the top of your pen.
  2. Remove both caps from the needle.
  3. Turn the dose selector at the bottom of the pen until you hear two clicks.
  4. With the needle pointed upwards, tap the pen a few times to collect air bubbles.
  5. Press the dose selector until it stops. If done correctly, you should see a small drop of liquid at the top of the needle and you should see ‘0’ in the dose window.

Once your pen is primed, you can safely inject the medicine.

Injecting Mounjaro: step-by-step instructions

Each pen contains four doses, and a new needle should be used for each one. To use the pen safely, make sure to follow these steps:

The injection usually takes around 10 seconds, and the process is easy once you know how to do it.

Step-by-step demonstration of the Mounjaro injection pen technique

Remember

Mounjaro is taken once weekly. Try to take it on the same day each week to help keep your routine consistent.

What you might feel during the injection

The injection is most commonly described as feeling like a small pinch or mild sting that lasts only a few seconds. In my experience, most people are relieved once they've done it for the first time.

Some normal reactions after the injection may include:

  • mild redness at the injection site
  • slight swelling
  • a small drop of blood
  • minor bruising

These effects are usually mild and disappear within a short time.

What not to worry about

When people give their first weight loss injection, they often notice small things and wonder if they’ve done something wrong.

I hear this a lot, and I want to reassure you that in most cases, these are completely normal:

  • a tiny drop of medicine on the skin after the injection
  • mild soreness at the injection site
  • a small air bubble in the pen
  • a small red mark after removing the pen

If you are unsure about anything, contact your prescriber for advice.

If you miss a dose

If you miss a scheduled dose of Mounjaro, you can still take the injection if less than 4 days have passed since the missed dose.

If more than 4 days have passed, skip the missed dose and take your next injection on your usual scheduled day.

You should never take two doses at the same time, and do not take more than one dose within the same week.

When to contact a doctor

While some mild discomfort is usually nothing to worry about, some reactions may require medical help. Contact a doctor or healthcare provider if you experience:

  • severe or persistent pain at the injection site
  • signs of infection (such as warmth, pus, or increasing redness)
  • severe allergic symptoms
  • unusual or severe side effects

If you are unsure whether something is normal, it is always safest to seek medical advice.

Remember…

  • Giving yourself an injection for the first time can feel unfamiliar, but most people quickly become comfortable with the process.
  • Take your time, follow the steps carefully, and remember that the injection pen is designed to make the process as simple as possible.
  • If you ever feel unsure about how to use your medication, you can always reach out to your healthcare provider for some additional assistance or advice. Remember, we’re here to help.

Also Read: Foods to Avoid During Weight Loss Treatment: A Practical Guide

Frequently asked questions

Does Mounjaro hurt?
How long should I hold the Mounjaro pen in place?
What if I inject incorrectly?
What if I see a small drop of blood?
What if liquid leaks out?
What if I hit muscle?
Can I inject it if the liquid is cold?
What if I feel anxious about needles?
Can someone else inject it for me?
Is there a secret 5th dose, or “golden dose”?
Medically reviewed by Dr. Caroline Fontana Written by our editorial team Last reviewed 07-05-2026

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