Mounjaro Pen Malfunction: What to Do If Your Mounjaro Pen Isn’t Working
- Written by Laura Pandolfi
- 📅 Last Updated:
- ⏱️ Read Time: 12 min
⚠️ Medical Disclaimer: This article is for informational purposes only. Always consult a healthcare professional for medical advice.
Key Takeaway
Most of the time, using a Mounjaro pen is straightforward. You unlock it, press, hear the clicks—and that’s it.
But when something doesn’t happen the way it should, it can feel very different.
No click.
No injection.
Something feels off.
And suddenly you’re left wondering:
“Did I get my dose? Should I try again? Is this Mounjaro pen broken?”
If that’s happened to you, you’re definitely not alone.
Mounjaro pens are designed to be simple and reliable—but like any medical device, malfunctions can happen.
The important thing is knowing what’s normal, what’s not, and what to do next
First, a Quick Reminder: How the Mounjaro Pen Should Work
Before assuming something is wrong, it helps to quickly go back to the basics.
With the Mounjaro pen (USA version), the process is simple:
- remove the cap
- place the pen flat against your skin
- unlock it
- press and hold the injection button
You should hear two clicks :
- the first = injection starts
- the second = injection completes
Then you wait about 10 seconds before removing it.
Photo Credits @Eli Lilly
👉 If you want a full step-by-step refresher, you can check our guide on how to inject Mounjaro correctly using the pen, which helps avoid confusion in moments like this.
Common Mounjaro Pen Malfunctions
When something feels wrong with your Mounjaro pen, it usually falls into a few common situations.
Sometimes the pen doesn’t click at all, which makes it unclear whether anything was delivered.
Other times, it clicks once—but not twice—leaving doubt about whether the full dose was injected.
You might also find that the unlock button doesn’t turn, which means you can’t even start the injection.
In some cases, the pen seems to activate, but no medication comes out, or only part of the dose is delivered.
And occasionally, people notice leaking medication, or a pen that feels jammed and doesn’t move properly.
None of these situations are normal—but they do happen.
Before Assuming It’s Defective, Check These First
Not every issue means your Mounjaro pen is broken.
Sometimes, it comes down to a small detail that’s easy to miss—especially if you’re distracted or in a hurry.
Take a moment to check:
- Is the pen fully unlocked?
- Is it pressed flat against your skin?
- Are you holding the button long enough?
- Are you following the steps in the correct order?
It might sound simple, but these small things can make a difference.
If everything looks correct, you can try once more.
If it still doesn’t work, then it’s time to treat it as a possible Mounjaro pen malfunction.
👉 If You’re Traveling, These Issues Can Be More Common. Many Mounjaro pen issues happen while traveling—when routines change, temperatures vary, and conditions aren’t as controlled. If you’ve experienced problems on the go, our guide on traveling with Mounjaro safely can help you avoid situations that may affect your pens.
What NOT to Do: Never Try to Fix or Open a Defective Mounjaro Pen
This is really important. When a Mounjaro pen doesn’t work, it can be tempting to try to “save” the medication—especially given the cost of tirzepatide injections.
Some people consider opening the pen and extracting the liquid manually, with a syringe for example. This is NOT safe.
The Mounjaro pen is designed to deliver a very precise dose of tirzepatide. Once you open it, there’s no reliable way to measure that dose correctly.
There’s also a risk of contamination, which can lead to infection.
And on top of that, the medication itself is sensitive to air and temperature changes.
So even if it feels frustrating, the safest approach is always the same:
Don’t try to fix it.
Don’t try to improvise.
✅ Quick Troubleshooting Checklist (Before Replacing Your Pen)
So What Should You Do Instead?
If your Mounjaro pen isn’t working, the best approach is simple. Run through this quick checklist:
- Is the pen unlocked fully before pressing?
- Is the base firmly pressed flat against your skin?
- Did you press and hold long enough (at least 10 seconds)?
- Did you hear two clicks (start and end)?
- Is the grey plunger visible after injection?
- Is there any visible damage or leakage?
If one of these steps was missed, you can try again once.
If everything is correct and it still doesn’t work, treat it as a defective Mounjaro pen. Stop and don’t keep trying multiple times.
Then, reach out to your pharmacist or healthcare provider for guidance. And in many cases, you’ll be able to get a replacement Mounjaro pen (see below).
👉 And because many of these issues are linked to storage conditions, it’s worth taking a step back and looking at your daily routine. Small details—like where you place your pen in the fridge or how you store it during the day—can make a real difference. You can read our full guide on how to store Mounjaro properly to make sure you’re protecting your medication in the best way possible.
Getting a Replacement for a Defective Mounjaro Pen
If your pen is truly defective, the manufacturer—Eli Lilly—may be able to help.
In the United States, you can contact their support line: 1-833-807-6576 or report a product concern online here.
They may ask for:
- the lot number of the pen
- details about what happened
- when and how the issue occurred
It’s worth keeping the pen and packaging until the situation is resolved.
When out or traveling, always carry your Mounjaro pens in an insulated travel cooler designed for medications.
Common Mistakes That Can Look Like a Defective Mounjaro Pen
Before jumping to the conclusion that the pen is faulty, it’s worth knowing that some situations can feel like a malfunction—but aren’t.
One of the most common is not pressing the pen firmly enough against the skin. The device needs proper contact to activate correctly.
Another is releasing the button too early. Even if you hear the first click, the injection isn’t complete until the second one—and that takes a few seconds.
It’s also easy to forget to fully unlock the pen, especially if you’re new to using Mounjaro pens.
And sometimes, people don’t feel the injection at all, which can be surprising. But that doesn’t necessarily mean it didn’t work.
If you heard both clicks and can see the grey plunger, the dose was delivered—even if you didn’t feel anything.
👉 If you’re ever unsure whether your pen is still safe to use, it’s not always just a malfunction question—it can also be about time. Mounjaro doesn’t last forever once it’s out of the fridge, and it’s not always obvious when it’s no longer effective. Our guide on expired Mounjaro pens and how long they remain safe to use helps you understand the limits and what to do if you’re unsure.
Final Thought: It Happens—And You’re Not Alone
A Mounjaro pen malfunction can feel stressful in the moment. But it doesn’t mean you’ve done anything wrong. These things happen, even when you follow all the instructions carefully.
The most important thing is not to panic, and not to take risks trying to fix it yourself. There’s always a safe next step—and usually, a solution.
FAQs About Mounjaro Pen Malfunctions
- How do I know if my Mounjaro injection worked?
You should hear two clicks—one at the start and one at the end. After your injection, check for the grey plunger inside the pen. If both are present, the dose was successfully delivered.
- What if my Mounjaro pen only clicked once?
If you only heard one click, the injection may not be complete. Do not try to inject again immediately without guidance. Contact your pharmacist or healthcare provider for next steps.
- Is it normal not to feel the Mounjaro injection?
Yes, it’s completely normal not to feel anything when injecting Mounjaro. The pen is designed to minimize discomfort during injection. If you heard both clicks and see the plunger, it worked.
- What should I do if my Mounjaro pen is jammed?
If the pen doesn’t click or move at all, stop using it. Do not force it or try to open it. Treat it as a defective Mounjaro pen and request a replacement (see above)
- Can bubbles in a Mounjaro pen cause a malfunction?
Small air bubbles are usually not a problem. They do not affect the dose or how the pen works. However, large bubbles or unusual appearance should be checked with a pharmacist.
What if medication leaks from my Mounjaro pen?
Leaking can indicate a damaged or defective pen. You may not receive the full dose if leakage occurs. Do not use it again and contact your pharmacy.
- Can I reuse a Mounjaro pen if it didn’t work?
No, you should not reuse a malfunctioning Mounjaro pen. Even if it partially worked, the dose may be incorrect. Always replace it to ensure proper treatment.
- Is there a reset button on a Mounjaro pen?
No, Mounjaro pens do not have a reset function. If something goes wrong, it cannot be corrected manually. The pen should be replaced if it malfunctions.
- Can temperature cause a Mounjaro pen to malfunction?
Yes, extreme heat or cold can affect Mounjaro pen. Temperature changes can impact both the device and medication. Always store it within the recommended temperature range.
💬 We’d Love to Hear From You
Have you ever had a Mounjaro pen malfunction? What happened—and how did you handle it? Sharing your experience can really help others who find themselves in the same situation. Feel free to leave a comment below!
⚠️ Medical Disclaimer
The information presented in this article and its comment section is for informational purposes only and is not intended as a replacement for professional medical advice. Always consult with a qualified healthcare provider for any medical concerns or questions you may have.
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Comments
4AllFamily Customer Care said:
Hi Sheryl,
We’re really sorry to hear about the issues you’ve had with your Mounjaro pens. Unfortunately, we’re not affiliated with the manufacturer or pharmacy, so we don’t have the ability to replace products or handle customer service for the medication.
We’d recommend reaching out directly to the pharmacy where you filled your prescription or to Eli Lilly (the manufacturer of Mounjaro) for support. They should be able to look into the issue with your pens and advise you on the next steps.
We know how frustrating this situation must be, and we hope you’re able to get it resolved quickly.
Warm regards,
4AllFamily USA Team
Sheryl Jaber-Klosterman said:
I had two pens that didn’t work, so I called for replacement pens, They informed they would’t replace them because I have gotten two other replacement ones, for being such a big company you would stand behind their product, it was not my fault they didn’t work, I need to switch products I would not give them a good review considering they don’t stand behind their product!!!! Sheryl Jaber-Klosterman 641-640-7830
4AllFamily Customer Care said:
Hi Ronald,
We’re really sorry to hear about the issues you’ve had with your Mounjaro pens. Unfortunately, as we’re not the manufacturer or pharmacy, we’re unable to replace the pens or provide you with more technical information here.
We recommend reaching out to their Mounjaro Patient Support via their contact page or calling 1-800-LILLY-RX (1-800-545-5979) during business hours, selecting the option for product complaints. If you’re still having trouble, you might want to ask your doctor or pharmacist to escalate the issue on your behalf, as they often have direct connections with the manufacturer.
We hope you get the help you need and that this issue is resolved soon.
Warm regards,
4AllFamily
Ronald Kincheloe said:
I am paying $50. Dollars a pen. And the last two out of four didn’t work. Thats a $100. Dollar out the window and when you’re on a fixed income it hurts. So how do l get a replacement for the two that didn’t work???
4AllFamily Customer Service said:
Hi Tammy,
We’re so sorry to hear what you’ve been going through—that sounds incredibly frustrating and concerning, especially when you’ve been using Mounjaro without issues until now. You’re absolutely right to stop using the remaining pens if you’re unsure of their reliability.
Unfortunately, since we’re not the manufacturer or pharmacy, we can’t directly replace pens or access your prescription records. However, you’re not alone—this kind of malfunction has been reported by others too, and Eli Lilly (the manufacturer) should definitely be made aware.
We recommend trying to reach them through their Mounjaro Patient Support contact page or calling 1-800-LILLY-RX (1-800-545-5979) during business hours and selecting the option for product complaints. If you’re still unable to reach them, consider asking your doctor’s office or pharmacist to escalate the issue on your behalf—they often have direct contacts with pharmaceutical reps.
We really hope you get the support you need and that this is resolved quickly.
—The 4AllFamily Team
4AllFamily Customer Service said:
Hi Tina,
Thanks for sharing your experience—you’re definitely not alone. We’ve heard from several users who’ve had similar issues with the second click not happening during injection. It can be really concerning, especially when you’re following all the instructions correctly.
The second click is supposed to confirm that the injection is complete, but if it doesn’t happen—even after holding the button down for over 10 seconds—it could indicate a malfunction. We recommend contacting the manufacturer, Eli Lilly, directly to report the issue. They may be able to provide a replacement and investigate the problem further.
You’re doing everything right by checking and reaching out. We hope you get a quick resolution!
—The 4AllFamily Team
4AllFamily Customer Service said:
Hi Michelle,
We’re really sorry to hear about your experience—how frustrating that must be, especially given the cost of Mounjaro pens. While we don’t manufacture the medication or devices, we totally understand your concern and you’re not alone—several users have reported similar issues.
If the pen won’t advance or dispense the medication properly even after replacing the needle, we strongly recommend reaching out directly to the manufacturer, Eli Lilly. They may be able to replace faulty pens or offer guidance on what to do next. Your pharmacy might also be able to assist or escalate the issue.
We hope you’re able to get a resolution soon—no one should have to waste such an important (and expensive) treatment.
Take care,
—The 4AllFamily Team
4AllFamily Customer Service said:
Hi Michael,
Thanks for your comment! We’re not medical professionals, so we always recommend checking with your healthcare provider or pharmacist to be sure. That said, it’s normal for the Mounjaro pen to still contain medication even if it’s not clearly visible in the glass window. As long as you hear the click and follow the instructions for use, the dose should be delivered properly.
If you’re ever unsure whether the pen is working or if the dose is being administered correctly, your doctor or pharmacist can walk you through a test dose or check the pen with you. You’re not alone—this is a common concern for many users.
Take care, and feel free to reach out if you have more questions!
—The 4AllFamily Team
Michael said:
I have a 15mg quick pen injecting 2.5mg to make it last. I can’t see liquid in the glass when I load it so I don’t know if it’s working or not. Any help would be appreciated
Tina Cochrane said:
just had 2 pens now not do 2nd click . I thought maybe something wrong I’m holding button down over min nothing I chk internet see if this is me doin wrong no is seems be big problem.
Tammy Harrison said:
I have used Mounjoro for several months with no problems. I recently obtained a new pack of four pens and two of the four did not work as usual. The first one did not “click” at all and when I removed it from my abdomen, the contents sprayed on top of my foot. I used a second one just so that I can remain in schedule and it did the same thing, only it sprayed in the air. I received none of the medication either time. I contacted the pharmacy where I obtained the prescription and I was told to contact the manufacturer because there is nothing they could do
I have called your company three times since 05/04/25 and cannot get passed the automated system. I am already off schedule now and I am pen pens short for this month. Please advise how I can have the two pens replaced. I don’t want to try the remaining two from this prescription. Thank you
Michelle Commerford said:
This is the second monjaro pen that has no budged and impossible to wid out. This is too expensive to just throw away and from what I read and the amount of people having issues with these pens yet there is zero accountability taken. I have been using these pens for 5 months now and am not doing anything different I have attached a nother needle making sure it is straight still unable to wind the damned thing out it won’t budge.
4AllFamily Customer Care Team said:
Hi Janine, thanks for your comment. We’re sorry to hear your Mounjaro pens malfunctioned. If the medicine was squirting and the second click didn’t happen, the pens may be defective. We recommend contacting your pharmacist or the manufacturer (Eli Lilly) as soon as possible—they can assist with a replacement and report the issue.
4AllFamily
Janine Zimmerman said:
I have 2 of my Mounjaro shots that have malfunctioned and medicine was squirting everywhere. It did not click on the 2nd click.
4AllFamily Customer Care Team said:
Hi Tim,
Thank you for sharing your experience with us. We’re sorry to hear about the malfunctions you’ve encountered with your Mounjaro pens. This is certainly unusual, and we had not previously heard of this specific issue. It might be helpful to report these incidents to the manufacturer or your pharmacy. They can provide guidance and potentially replace the malfunctioning pens to ensure you can continue your treatment without further issues. Documenting such malfunctions helps improve product quality and user safety.
Best regards,
4AllFamily
4AllFamily Customer Care Team said:
Hi Brenda,
I’m sorry to hear about the issue you experienced with your Mounjaro pen. Unfortunately, as we are not the manufacturer, we are unable to provide replacements. I recommend contacting the manufacturer’s customer service or your pharmacy as soon as possible to report this malfunction and inquire about getting a replacement for your Mounjaro pen. They should be able to assist you in ensuring you have the medication you need for your next dose.
Best regards,
4AllFamily
Brenda said:
I have been taking my shot and my stomach and I decided to switch to my thigh and when I went to take the shot it misfunctioned and the medication went squirting everywhere. I would like to find out if you will do replacements? I was supposed to take another shot and I’m not going to have enough now.
Tim Black said:
I have had two malfunctions that are not listed here. When removing the cap and preparing for an injection, the mechanical part of the pen came off with the cap. That injection didn’t work, so I tried my other and final injection. The same thing happened again. In both cases, I tried to repair the pens, but I couldn’t get the broken part out of the cap. I could have used pliers, but that would destroy the part. I have been using Mounjaro for many months, and this is the first time it has malfunctioned…twice.
4AllFamily said:
Hi Teena,
We’re really sorry to hear about your frustrating experience with the Mounjaro injectors. That sounds incredibly stressful, especially when dealing with a medication you rely on.
If you’re experiencing repeated issues with multiple injectors, it might be helpful to check in with your doctor or a nurse to ensure everything is being administered correctly. Sometimes, injection technique can make a difference, and a healthcare professional could provide guidance to help avoid wasted doses.
That said, it’s disappointing to hear about the difficulties with replacements. We understand how important every dose is, and we hope Eli Lilly can provide a better resolution for situations like this in the future. In the meantime, you might also want to check with your pharmacist or insurance provider to see if they have any suggestions for addressing this issue.
Wishing you the best, and we hope everything gets sorted out soon!
4AllFamily Customer Care Team
Teena Selzer said:
I have experienced defective Mounjaro injectors twice now. In January, 2025 I attempted to take my weekly dose and ended up going thru 4 injectors (same box) before the 5th injector pen worked properly. I contacted Eli Lilly and they replaced the box. A month later, the same thing happened. This time I had to go thru 8 injectors (all the same lot number) before the 9th one worked. I contacted Eli Lilly again and they indicated that they will replace 1 box of injectors but refused to place the 2nd box since they replaced a box in January. A reputable company like Eli Lilly is refusing to back their defective injectors. I am a senior citizen living on a limited income. Every penny I spend counts. Besides that, how am I supposed to go without 1 month of medication? I spoke to one of their Reps today who informed me of their decision. When I asked her that same questions she said that some medications stay in your body for a month. I was surprised that she was indicating it would be alright to go without the medicine for that period of time. What will I do if this happens again? Eli Lilly does not stand behind their products.
4AllFamily Customer Care Team said:
Dear Jennifer,
Thank you for reaching out and sharing your concerns regarding your Mounjaro pen. We understand the frustration and distress caused by the lack of response you’ve experienced.
However, we would like to clarify that our blog is an independent platform and is not affiliated with the manufacturer of Mounjaro.
For assistance with your Mounjaro pen, we recommend contacting the manufacturer’s customer support directly. You can reach them at:
Lilly Support Service at 1-800-LillyRx (1-800-545-5979)
MOUNJARO.LILLY.COM
We hope this information helps you resolve the issue promptly. If you have any other questions or need further assistance, please feel free to reach out.
Best regards,
4AllFamily
Jennifer said:
My pen will not release the next does. The pharmacists looked at it and lodged a fault notice with your company about two weeks ago now. I have provided all my contact information. No one has contacted me. I have called the number myself to lodge fault and again have left my name and email.
Again no response from your company regarding faulty pen. Please reply to your customers as this medication is expensive and when the pen is faulty this costs me money, time and distress. Please respond to me.