How to Inject Mounjaro in 8 Easy Steps 

The thought of injecting Mounjaro for the first time might seem daunting – but it doesn’t need to be!  

The Mounjaro KwikPen is safe and easy to use in the comfort of your own home. Each pen contains four doses, with you injecting one dose a week. This means one pen will last you roughly a month.  

If you’re unsure of how to inject Mounjaro, we’re here to take you through what you need to do step-by-step.  

Three key takeaways 

• Always read the instruction leaflet and patient information leaflet before injecting Mounjaro for the first time.  
• You must use a new needle every time you inject Mounjaro. 
• You must prime your pen every time you inject Mounjaro, not just the first time using a new pen.  

Where to inject Mounjaro 

When choosing the best place to inject Mounjaro, you have three sites to pick from: 

• your stomach (abdomen) 
• your thigh 
• the back of your upper arm 

No site is less painful than the other. So, where you choose is down to what you feel most comfortable with.  

If you choose your upper arm, you’ll need someone else to inject for you. This might make it a good choice for your first injection, if you’re feeling a bit nervous about doing it yourself.  

It’s important to then rotate sites between doses, in order to try and minimise irritation, and any potential side effects of Mounjaro. 

Preparing for injection 

Step 1: Check the pen 

Before injecting Mounjaro, you need to make sure that you’re using the right pen, and that there are no signs of damage. Check that:  

• the medication name and dose strength matches your prescription 
• the pen is not expired or damaged 
• the liquid isn’t cloudy 
• the pen doesn't contain bits 
• the medication isn’t frozen 

If you notice any issues with your pen, do not use it. However, it is normal for you to see some small air bubbles in your pen. 

Step 2: Wash your hands 

You should be injecting your Mounjaro pen with clean hands, so wash your hands thoroughly with soap and water. You could also consider using an anti-bacterial hand sanitiser to disinfect your hands. Clean hands reduce the risk of you getting infection at the injection site. 

You may also want to have some gauze or a cotton ball to hand, in case there’s a bit of blood when you remove the needle.  

Step 3: Attach the needle 

You then need to attach the needle. You should always select a new needle for each injection to prevent infections or blocked needles. 

To attach a new needle: 

1. Remove the pen cap.  

2. Wipe the inner red seal of the pen with a swab.  

3. Select a new needle and remove the paper tab from the outer needle shield. 

4. Push the capped needle straight onto your pen and twist the pen until it’s tight. 

5. Pull off the outer needle shield, and set it to one side.  

6. Pull off the inner needle shield and dispose of it. 

Step 4: Prime the pen 

Next, it’s time to prime your pen: 

1. Slowly turn the dose knob until you hear two clicks. If your pen is correctly primed, the extended line in the dose window should align with the dose indictor. You can turn the dose knob either way to make sure it becomes aligned.  

2. Hold your pen with the needle upwards. 

3. Gently tap the cartridge holder to collect air bubbles at the top. 

4. Release some of the medicine into the air by pushing the dose knob until it stops, then count to five slowly while holding the dose knob. Check to make sure that the ‘0’ icon is showing in the dose window, but do not inject yourself yet. 

If you don’t see a small amount of medicine, come out of the tip of the pen then you’ll need to repeat the priming steps again. Do not repeat the steps more than twice. 

If you still don’t see any medicine after two more attempts, then you need to change the pen needle and begin again. 

You must do this process every time you inject yourself, not just between pens.  

Ready to inject 

Step 5: Choose your injection site 

Pick between your stomach, thigh, or upper arm. Remember, if you choose your upper arm, someone else will need to inject for you – make sure they wash their hands first!  

It’s recommended that you rotate your injection site week-to-week. For example, if last week you injected in your thigh, this week consider your upper arm or stomach.  

You can inject into your stomach across consecutive weeks, but you need to make sure it is in a different area of your abdomen. And any injection should be least two inches away from your belly button. 

Step 6: Inject the needle 

Turn the dose knob until it stops, and the ‘1’ icon is on display. Then insert the needle into your skin. 

To actually inject Mounjaro, push the dose knob until it stops. Count to five slowly, while keeping hold of the dose knob. 

Step 7: Remove the needle 

Once you finished counting to five, you can pull the needle out of your skin. Check that the dose window now shows ‘0’. This means you’ve received the full dose.  

If ‘0’ isn’t showing, you’ll need to apply a new needle, reinsert into your skin and keep pushing the dose knob until you see ‘0’. Do not redial the dose knob.  

If, after a second attempt, you still can’t see ‘0’ in the dose window, do not try again.   

If you see a bit of blood at the injection site once the needle is out of your skin, press on the injection site with gauze or a cotton ball.  

Step 8: Dispose of the needle 

After your injection, carefully replace the outer needle shield that you’ve put to one side. Unscrew the capped needle and dispose of it instantly into a sharps bin. 

Do not dispose of your needles in your household waste bin as this can cause cross-contamination. And do not store the pen with the needle attached. 

Next, replace the pen cap. You must not store it without the pen cap attached. While your unopened Mounjaro pens should be stored in the fridge, you can store open pens at room temperature (no higher than 30°C) for up to 30 days. 

Once you're done with your monthly KwikPen, dispose of the pen separately to your needle in your regular household bin. 

4 tips for injecting Mounjaro safely 

To stay safe and comfortable when injecting Mounjaro every week, we recommend that you: 

• inject at the time of day each week 

• make sure you’re consistent with rotating your injection sites 

• let your Mounjaro pen come up to room temperature before use 

• consider using a numbing cream, like EMLA, at the injection site before injecting to reduce any discomfort 

Looking after yourself post-injection 

“It’s important to look after yourself post-injection, as you might feel a bit sore. Keep some gauze or cotton balls to hand in case you have a bit of bleeding after removing the needle, but make sure to gently press on the site rather than rub it.  

“To help reduce any skin irritation, you could take an antihistamine tablet or use an antihistamine cream. Over the counter pain relief can also help if you’re feeling uncomfortable post-injection.  

“As for side effects, bland foods and smaller meals can help combat nausea, while it’s important to stay hydrated if you experience diarrhoea while on Mounjaro. 

“Above all else, give yourself the time and space you need to adjust post-injection, especially if you’ve recently increased your Mounjaro dosage.” 

Jason Murphy, Head of Pharmacy at Chemist4U 

Watch our video for help on injecting Mounjaro

Frequently asked questions about how to inject Mounjaro 

Is it better to inject Mounjaro in your stomach or your thigh? 

Mounjaro works just as well if you inject in your stomach or your thigh, so your choice of injection site is down to your individual preference and comfort.  

Can you inject Mounjaro twice a week? 

No, you should not inject Mounjaro twice a week. Its doses are designed to be injected once a week, on the same day every week.  

What happens if you inject Mounjaro into muscle? 

Mounjaro is designed to be injected under the skin (your subcutaneous tissue), and not directly into muscle. Injecting into muscle may be more painful, and can make side effects more likely, as the medication will be absorbed too quickly.  It may also reduce the effectiveness of Mounjaro when it comes to weight loss.  

Can you inject Mounjaro straight from the fridge? 

While you can inject Mounjaro straight from the fridge, it isn’t recommended. Letting your pen come up to room temperature for 30 minutes can reduce your discomfort when injecting.  

How do I know if I’ve injected Mounjaro correctly? 

You’ll know that you’ve injected Mounjaro correctly if the dose window turns from ‘1’ to ‘0’ after you’ve inserted the needle, pushed the dose knob until it stops, and help it for five seconds.  

Sources 

• Instructions for Use of Mounjaro KwikPen. Eli Lilly. [Accessed 4 February 2026].