If your Mounjaro pen is stuck, jammed, or will not inject, you want practical help rather than complicated explanations. This guide covers some common things to check, what to do if the pen still does not work, and how to deal with a potentially faulty pen. It also answers one common question: whether the Mounjaro pen has a reset button.
If a pen does not work as expected, the issue may be related to the priming process, the needle, or the way the pen is being used. Work through the checks below carefully and follow the Instructions for Use supplied with your pen. If the problem continues, do not force the pen. Contact your pharmacy or healthcare professional for advice.
A note before you start: this guide covers the multi dose Mounjaro KwikPen supplied in the UK, which is designed to provide four weekly doses. Your Instructions for Use leaflet is the most important reference for your specific pen, so check it before troubleshooting.
First, a Myth to Clear Up: There Is No Reset Button
If you are searching for a "Mounjaro pen reset button" or wondering how to reset the pen, the Mounjaro KwikPen does not have a reset button. There is no button or setting that resets the pen if it becomes difficult to operate.
If your pen is not working as expected, the safer approach is to check the instructions and the usual injection steps rather than trying to reset, dismantle, or modify the pen. If the problem cannot be resolved, contact your pharmacy or healthcare professional for advice.
So, if you are asking "how do I reset my Mounjaro pen?", there is no reset procedure to follow. You can check the points below, but do not force the pen if it remains stuck.
First, Is It Actually Stuck?
There are two simple things to check before assuming your pen is faulty.
Have you used all four doses? The Mounjaro KwikPen is designed to provide four weekly doses. If you have already used all four doses and the pen will not provide another dose, it may simply be finished rather than stuck. You may still see some liquid in the pen. Do not try to remove or use leftover medicine. Follow the instructions for disposing of the pen and use a new one when appropriate.
Is a needle attached? The KwikPen needs a new needle to be fitted for each injection. If there is no needle attached, or if the needle is not fitted correctly, the pen may not work as expected.
If neither of these explains the problem, check the following steps and refer to your Instructions for Use as you go.
Step by Step: What to Check if Your Mounjaro Pen Is Jammed
Work through these checks carefully and stop if the pen still does not operate as described in your Instructions for Use. Do not force the pen.
Step 1, Check the Priming Process
Priming is an important part of using the Mounjaro KwikPen and should be completed according to the manufacturer's instructions before each injection.
The priming process helps prepare the pen for the injection and helps check that medicine can flow through the needle. Follow the exact priming steps in your Instructions for Use, including the correct position of the pen and the amount you are instructed to turn and press the dose knob.
If the pen does not prime as described in the leaflet, do not keep forcing the dose knob. Move on to checking the needle and contact your pharmacy or healthcare professional if the problem continues.
Step 2, Check the Needle
A needle that is blocked, bent, damaged, or incorrectly fitted can affect how an injection pen works.
- Use a new sterile needle for each injection.
- Make sure the needle is securely attached and appears straight and undamaged.
- If you think the needle may be blocked or damaged, replace it with a new needle as described in the Instructions for Use.
- Make sure the required needle shields have been removed before the injection, following the manufacturer's instructions.
Do not try to unblock a needle with another object or continue using a damaged needle.
Step 3, Press the Dose Knob Slowly
If the dose knob feels difficult to press, do not force it. Follow the injection instructions supplied with your pen and use a slow, steady movement.
The manufacturer provides specific instructions for positioning the pen and pressing the dose knob during an injection. Follow those instructions rather than trying to change the technique yourself.
The dose window should show the position described in the Instructions for Use after the dose has been delivered. If the pen does not operate as expected or you are unsure whether you received the full dose, do not take another dose to compensate. Contact your healthcare professional or pharmacy for advice.
Step 4, Check the Medicine and the Pen
- The medicine should normally appear clear and colourless to slightly yellow. Do not use the pen if the medicine looks cloudy, has changed colour, or contains particles.
- Check the pen for visible damage before use. If it appears damaged, do not use it and contact your pharmacy for advice.
- Do not use the pen if it has been frozen. Follow the storage instructions supplied with your medicine.
- If you notice anything unusual about the pen, such as damage, leakage, or another problem that is not covered by the Instructions for Use, do not try to repair it yourself. Contact your pharmacy or healthcare professional for advice.
What Not to Do
If your Mounjaro pen is difficult to use, avoid trying to fix it yourself. These steps are important for using the pen safely.
- Do not force a jammed pen. Forcing the dose knob may damage the pen or affect dose delivery.
- Do not try to remove leftover medicine from a finished pen. Do not use a syringe or another method to extract it. Any remaining liquid is not intended to be used as an additional dose.
- Do not take the pen apart or try to find an internal "reset". The pen is not designed to be repaired or reset by the user.
- Do not reuse a needle or operate the pen without a needle attached. Use a new needle for each injection and follow the Instructions for Use supplied with your pen.
- Do not take another dose if you are unsure whether the previous dose was delivered. Taking another dose could result in you receiving more medicine than prescribed. If you are unsure, check the dose window if possible and contact your pharmacy or healthcare professional before taking any more Mounjaro.
When the Knob or Top Comes Off: A Word on Fake Pens
There is an important safety point to know if the dose knob or another part of your Mounjaro pen detaches during use.
In February 2026, the MHRA reported falsified Mounjaro 15mg pens in the UK supply chain. The reported pens were identified because the dose knob came off during use. Testing found that the pens contained tirzepatide, but they did not meet the required manufacturing and safety standards.
If the dose knob or top of your pen comes off unexpectedly, do not continue using the pen. Instead:
- Stop using the pen.
- Contact the pharmacy that supplied it and explain what happened.
- Check that the medicine came from a legitimate, GPhC registered pharmacy.
- Consider reporting a suspected falsified or defective medicine through the MHRA Yellow Card scheme, following the current reporting guidance.
- Keep the pen and its packaging until you have received advice, unless you are told otherwise.
A problem with a pen does not automatically mean it is counterfeit. Genuine devices can also have faults. However, if a component detaches unexpectedly, it is safer to stop using the pen and have the issue checked rather than trying to repair or continue using it. Our guide to buying genuine Mounjaro covers how to check a pen is real.
Getting a Faulty Pen Replaced
If you have worked through the checks and your pen still does not work, it may be faulty. Do not try to repair it yourself. Contact the pharmacy that supplied it for advice about what to do next.
Start with the pharmacy that dispensed your pen. Explain what happened and tell them which troubleshooting steps you have already tried. They may ask whether the pen has been used, how it was stored, whether it was kept under the recommended storage conditions, and what problem you noticed.
You can also contact Eli Lilly, the manufacturer, for advice about the device. The UK contact details should be available in your Instructions for Use leaflet. If the issue cannot be resolved through the initial checks, your pharmacy can also advise you on the next step.
Keep the faulty pen rather than throwing it away. Store it safely and out of reach of children. The pharmacy or manufacturer may need to inspect it, particularly if a manufacturing fault is suspected. If you think the pen may be counterfeit, follow the advice provided by the MHRA or your pharmacy.
Will the pen be replaced? A genuine manufacturing fault may be handled by the pharmacy or manufacturer, but the outcome can depend on the individual circumstances, including how the pen was stored and handled. A webpage cannot guarantee that a replacement will be provided. The best approach is to contact the pharmacy that supplied the pen and explain the problem clearly. If you were supplied by EveryDayMeds, contact our pharmacy team and we can help you understand the next step.
Do not take an extra dose to make up for a missed injection. If a faulty pen means you miss your usual injection day while the issue is being resolved, contact your pharmacy or prescriber for advice on when to take your next dose.
"Reset" Versus "Restart": Two Different Questions
These two questions can sound similar, but they are about completely different things.
Resetting the pen is a device question. The Mounjaro KwikPen does not have a reset function, so there is no reset procedure to follow.
Restarting Mounjaro is a treatment question. This applies if you have stopped tirzepatide for a period of time and want to start treatment again. The appropriate dose after a treatment break can depend on how long you have stopped and your individual circumstances. Your prescriber can advise whether you should restart at the same dose or a lower dose.
Do not simply use an old pen and restart at your previous strength without checking with your prescriber, particularly after a longer break. If you have stopped Mounjaro and want to start again, speak with your prescriber rather than treating it as a pen troubleshooting issue.
If You Still Cannot Inject
If your Mounjaro pen still does not work after you have followed the troubleshooting steps, stop trying to force it. Repeated attempts could make the situation more difficult and may affect dose delivery.
- Contact your pharmacy. The pharmacy that supplied your pen can advise you on the next step and explain what to do if the pen appears faulty.
- Contact Eli Lilly. The manufacturer may be able to help troubleshoot the specific device. UK contact details are provided in your Instructions for Use leaflet.
- Do not take an additional dose to compensate. If you are unsure whether you received your prescribed dose, speak with your pharmacy or prescriber before taking more Mounjaro.
- Keep the faulty pen safely. Store it out of reach of children and follow your pharmacy's or manufacturer's advice about returning or disposing of it.
A pen that does not work as expected can be frustrating, but you do not need to try to repair it yourself. If the basic checks do not resolve the problem, getting advice from the pharmacy or manufacturer is the safer next step.
How Long Does a Pen Last?
This is useful to know because it can help you tell the difference between a finished pen and a pen that is not working as expected.
- Each KwikPen is designed to provide four weekly doses, so one pen is intended to cover four weeks of treatment.
- After four doses have been given, the pen is finished. It should not be used for another dose.
- Once first used, the pen should be discarded after 30 days, even if there appears to be medicine remaining, in line with the manufacturer's instructions.
- You may notice a small amount of liquid remaining in the pen after the scheduled doses have been used. This is expected and is not intended to be used as an additional dose.
If your pen has stopped working after you have received four doses, it may simply be finished rather than faulty. Use a new pen according to your treatment plan.
Preventing Common Issues with a Stuck Pen Next Time
A few simple habits can help you use your Mounjaro KwikPen correctly and avoid some common injection problems.
- Prime the pen before each injection, following the manufacturer's Instructions for Use.
- Use a new needle for every injection and attach it correctly according to the instructions.
- If the pen has been stored in the fridge, follow the manufacturer's instructions about when it can be used. Do not heat the pen artificially or use a heat source to bring it to room temperature.
- Press the dose knob slowly and steadily rather than forcing it.
- Store the pen according to the recommended storage conditions. Unused pens should generally be kept refrigerated between 2°C and 8°C, protected from light and never frozen. Follow the product instructions for storage after first use and the maximum temperature allowed.
How the Pen Works, Briefly
The Mounjaro KwikPen is a multi dose injection pen designed to provide four weekly doses. You attach a new needle, follow the priming instructions, prepare the prescribed dose and press the dose knob to give the injection under the skin. The dose window helps you follow the injection process.
You do not need to understand the internal mechanism to use the pen correctly. Follow the Instructions for Use supplied with your pen and do not try to take the device apart or modify it. If it does not work as described, contact your pharmacy or healthcare professional for advice.
Key Takeaways
- There is no reset button: the Mounjaro KwikPen cannot be reset.
- If the pen does not work as expected, check the needle and follow the priming and injection instructions.
- Use a new needle for every injection and follow the manufacturer's instructions for priming.
- Press the dose knob as instructed and never force the pen.
- A finished pen may contain some liquid by design. Do not try to extract or use the remaining medicine.
- If the dose knob or another part of the pen detaches unexpectedly, stop using it and contact your pharmacy.
- If the pen appears faulty, keep it safely and contact the pharmacy that supplied it for advice.
- Restarting Mounjaro after a treatment break is a clinical decision. Speak with your prescriber rather than simply restarting at your previous dose.