Mounjaro Injection Pen Jammed: Causes, Fixes, and How to Prevent It

Article Summary

• Mounjaro (tirzepatide) is a once-weekly injection used for weight loss and type 2 diabetes, helping control blood sugar and reduce appetite.
• A Mounjaro KwikPen can seem ‘jammed’ or ‘stuck’ through an oversight in how it’s used, or from mechanical failure.
• Best practice to prevent future ‘jamming’ issues includes consistency, proper storage and handling.

Why does my Mounjaro pen seem jammed?

Taking your Mounjaro injection on time is a critical part of managing your treatment.

When combined with a balanced diet and increased physical activity, Mounjaro could help you lose an average of 21% of your body weight, with some people achieving up to 25% (based on results from a 72 week trial). [1]

Consistency in administering your treatment is key, so finding that your Mounjaro KwikPen seems jammed can be frustrating and worrying.

You prepare your Mounjaro pen, press the injection button, but nothing happens. The dose knob won't turn, or the plunger doesn't move. While this experience is common, it rarely means the injection pen is permanently broken.

Mounjaro is a leading medication for managing type 2 diabetes and a highly effective option among injectable weight loss treatments. [2]

This guide will help you demystify why your Mounjaro KwikPen might seem stuck. From normal operation to rare malfunctions, we look at common causes, including simple oversights, that can help resolve any issues.

What does ‘jammed’ really mean for a KwikPen?

The term ‘jammed’ can describe several scenarios. It could mean the dose knob is difficult to turn, the injection button is hard to press, or no medication comes out when the button is pushed. Understanding the specific issue is the first step toward finding the right solution. In most cases, it's another issue that’s making the pen feel jammed, not a mechanical failure.

Understanding your Mounjaro KwikPen: What's normal vs. what's not?

Before troubleshooting, it's essential to have a baseline for how a Mounjaro KwikPen should look, sound, and feel during normal operation. If you're new to using the injection pen, it might seem like there's a problem with it even if it’s working normally.

Expected sounds and sensations during use

You prime the pen by moving it to the prime line (two clicks), and push down to check the flow of the pen. Then you dial up until you see 'one' in the dose window.

It's normal to feel some resistance when pushing the button. This is the activation mechanism working to push the liquid medication through a very fine needle. This resistance is a sign of proper function, not a jam.

Normal resistance vs. A stuck mechanism

A certain amount of pressure is required to press the injection button. This is normal. A ‘stuck’ or ‘jammed’ mechanism feels different. It feels like a complete blockage. If the button feels spongy or won't depress at all despite firm, steady pressure, there may be an issue with the internal mechanism, or the pen needle could be faulty, jammed or blocked. It’s also possible the needle may not be compatible with the pen. Forcing the button can damage the Mounjaro pen or cause injury.

Visual check: What to look for (and not worry about)

The Mounjaro liquid should be clear and colourless to slightly yellow. Don't be alarmed by a small air bubble in the pen cartridge. These small air bubbles are normal and will not affect your dose or cause harm if you prime the pen correctly. However, if the liquid appears cloudy, has particles, or is discoloured, don’t use the pen and contact your prescriber.

The most common culprit: Simple oversights

The vast majority of ‘jammed’ pen issues aren't due to a faulty device but rather a simple-to-fix user error. This is good news because it means you can likely solve the problem yourself without needing a replacement pen. Understanding some common pitfalls helps.

Is the pen truly empty?

The Mounjaro KwikPen contains enough treatment for four doses. As you use the pen, the plunger inside will move down the cartridge. If you can’t dial a dose, check to see if there is enough medication left. The pen is designed to prevent you from dialing a dose larger than the remaining amount of liquid. If only a small amount is left, you might not be able to dial your full dose, which can feel like the dose knob is jammed.

Remember that Mounjaro pens are designed to deliver precise doses of tirzepatide.

Mounjaro KwikPens contain 3 mL of liquid designed for exactly four doses of 0.6 mL each, plus a deliberate 'buffer' overfill to account for priming losses (ejecting air bubbles). The leftover liquid's concentration is unpredictable, and potentially too little (leading to possible underdosing and reducing effectiveness) or too much (leading to possible overdosing which heightens risks of side effects including nausea, vomiting, diarrhoea and constipation.)

If you can’t dial another dose but see leftover liquid, it’s because the pen has already delivered the intended amount per dose. The remaining liquid isn’t meant for use and is there for accurate priming.

Incorrect pen needle attachment

A properly attached pen needle is critical for medication flow. If the needle is screwed on crookedly or not tightened enough, the pathway for the medication could be blocked.

Similarly, if you forget to remove both the outer and inner needle caps before the injection step, the medication has nowhere to go, and the injection button will feel stuck. Always use a new pen needle for each injection and make sure it’s screwed on straight and securely.

Improperly priming the pen

With Mounjaro, priming is a mandatory step before every weekly injection. This removes air from the needle and cartridge and makes sure the pen’s working correctly. To prime, you dial two units, hold the pen with the needle pointing up, and press the injection button until you see a droplet of liquid.

If the pen is not primed, an air pocket can block the flow of medication, creating resistance that feels like a jam. Forgetting this step is one of the most common reasons for injection issues.

Improper injection technique

Proper injection technique is crucial. Insert the needle into your skin and inject the medication by pressing and holding the dose button until ‘0’ appears, then continue holding for five seconds to ensure full delivery. A slow, steady push at a 90-degree angle is more effective than a quick, hard jab.

How storage affects your Mounjaro KwikPen

How and where you store your Mounjaro pen can directly impact its function and the stability of the tirzepatide within. Store Mounjaro KwikPens in a refrigerator before first use (2 °C – 8 °C). Do not freeze. After first use, Mounjaro may be stored unrefrigerated for up to 30 days at a temperature not above 30 °C, and then the pre-filled KwikPen must be discarded.

Damage from mishandling or storage

Dropping your Mounjaro pen can damage it, even if there is no visible crack. Storing the pen with the needle still attached can allow air to enter the cartridge or medication to leak out, both of which can lead to problems with future doses. Always take the needle out immediately after your injection and store the pen with its cap on.

Why the KwikPen dose knob may be difficult to push

Here’s an at-a-glance guide to suspected issues:

• The needle may be faulty, jammed or blocked. It may not be compatible with the pen.
• There could be dust, food residue, dirt or liquid inside the KwikPen.
• It’s possible that you can be pushing the dose knob too quickly.

Remember to ensure proper injection technique, pen needle use and your dose delivery and priming technique. If you’ve received four full doses or primed more than eight eights times, you won’t be able to take another dose. Throw the KwikPen away and get a new KwikPen.

Conclusion

Encountering a Mounjaro KwikPen at home that seems jammed can be a stressful moment in your treatment journey, but it is rarely a sign of a defective device. By understanding the normal use of the pen, you can tell the difference between a minor hiccup and a genuine problem. The most common causes are often simple oversights that are easy to fix, such as a needle not being attached correctly, forgetting to remove both needle caps, or not priming a new pen.

Your first line of defence is to systematically troubleshoot by checking the medication, changing the needle, and reviewing your injection technique. Adhering to proper storage, handling, and the step-by-step instructions in the user manual will prevent the vast majority of issues from ever occurring.

If you’ve followed all these troubleshooting steps and your pen still doesn’t work, set it aside and use a new pen for your dose. Contact your clinician for advice if you have any concerns about your medication or device.

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References

1. Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine [Internet]. 2022 Jun 4;387(3). Available from: https://www.nejm.org/doi/full/10.1056/NEJMoa2206038
2. Patricia J Rodriguez, Brianna M Goodwin Cartwright , Samuel Gratzl, Rajdeep Brar, Charlotte Baker, Ty J Gluckman , Nicholas L Stucky. Semaglutide vs Tirzepatide for Weight Loss in Adults With Overweight or Obesity. PubMed [Internet]. 2024 Sep 1;184(9):1056-1064. Available from: https://pubmed.ncbi.nlm.nih.gov/38976257/