If your Mounjaro pen is stuck, jammed or will not inject, you probably want practical steps rather than a technical explanation. The UK Mounjaro KwikPen is a multi dose pen designed to provide four weekly doses. You attach a new compatible needle, prime the pen as described in the Instructions for Use, select the prescribed dose and press the dose knob to give the injection.
This guide is for people in the UK who use the Mounjaro KwikPen and need help when an injection does not go as expected. It explains some common things to check, what you should avoid doing, when to stop and ask for help, and how to reduce the chance of similar problems in the future.
A pen that does not seem to work does not necessarily mean that it is broken. Issues such as an incorrectly fitted or blocked needle, or not following the priming instructions, can affect how the pen works. Checking these points carefully can help you avoid unnecessary dosing problems. If your pen still does not work after following the manufacturer's instructions, do not force it. 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. Your Mounjaro Instructions for Use leaflet is the most important reference for your specific pen, so follow it alongside any advice from your healthcare professional.
First, Is It Actually Stuck?
Before troubleshooting, check two simple things.
Have you already used all four doses? The KwikPen is designed to provide four weekly doses. Once the intended doses have been used, the pen is finished. A small amount of medicine may remain in the pen, but you should not try to remove it or use it as an extra dose. Follow the manufacturer's instructions for disposal and use a new pen when your next dose is due.
Is a compatible needle attached? A new pen needle should be attached before each injection, following the instructions supplied with the pen. Do not try to use the pen with a needle that is blocked, damaged or not properly attached.
If neither of these explains the problem, work through the checks below and follow your Instructions for Use carefully.
Step by Step: What to Try
Work through these checks in order and stop if the issue is resolved.
Step 1: Prime the pen
Priming is an important part of preparing the KwikPen for an injection and should be done as described in the Instructions for Use. It helps prepare the pen and confirm that the medicine can flow through the needle.
Follow the exact priming steps in your leaflet, including the position of the pen and the amount of turning required. Do not try to remove air from the pen by opening it or drawing medicine into a syringe.
If you are unsure how to prime your pen, ask your pharmacist or healthcare professional to show you the correct method.
Step 2: Check the needle
A blocked, bent or incorrectly fitted needle can affect the injection. Using a new compatible needle for every dose can help avoid problems associated with needle reuse.
- Make sure you are using a new compatible pen needle and attach it as shown in the Instructions for Use.
- If you think the needle may be blocked or damaged, replace it with a new one rather than trying to unblock it.
- Check that the needle is securely attached and that you have removed the relevant needle shields before the injection.
- Never reuse a pen needle.
Step 3: Press the dose knob as instructed
If the dose knob feels difficult to press, do not force it. Follow the manufacturer's instructions for administering the dose and use a steady movement rather than trying to push the knob with excessive force.
Continue following the injection instructions until the dose has been delivered as described in your Mounjaro leaflet. If the dose knob will not move or the pen does not appear to deliver the dose, stop rather than repeatedly pressing or forcing it.
Mounjaro is administered as a subcutaneous injection. Follow the Instructions for Use for the correct injection technique and injection site.
Step 4: Check the medicine and the pen
- Check the medicine before use. Mounjaro should normally be clear and colourless to slightly yellow. Do not use it if it appears cloudy, has changed colour or contains particles.
- Check the pen for visible damage. Do not use a pen that appears damaged.
- Do not use Mounjaro if the pen has been frozen. Follow the storage instructions supplied with your medicine.
- If you notice something unusual with the pen, such as a damaged component or a problem that prevents normal use, do not force the device. Contact your pharmacy or healthcare professional for advice.
Mounjaro is designed for subcutaneous injection. The usual injection areas include the abdomen and thigh. The back of the upper arm may also be used when the injection is given by another person. Always follow the specific instructions provided with your pen and the advice of your healthcare professional.
What Not to Do
If your Mounjaro pen is not working as expected, it is important not to force or modify it.
- Do not force a jammed pen. This could damage the device or result in an incorrect dose.
- Do not try to extract leftover medicine from a finished pen, either with a syringe or by any other method. The remaining medicine is not intended to be used as an extra dose, and you cannot reliably measure the amount yourself.
- Do not take the pen apart or attempt to repair it yourself.
- Do not reuse a needle or use the pen without a needle attached. Use a new compatible needle for every injection and follow the Instructions for Use.
- Do not inject another dose if you are unsure whether the first dose was delivered. Taking another dose without checking could mean receiving more medicine than prescribed. Check the dosing window and contact your pharmacy or healthcare professional if you are still unsure.
When the Knob or Top Comes Off: A Word on Fake Pens
A pen that comes apart during use should be taken seriously, particularly if the dose knob or another important component becomes detached.
The MHRA has issued warnings about falsified Mounjaro products in the UK. If your pen behaves unexpectedly or appears different from the product shown in the official instructions, stop using it and check where it came from.
If the dose knob or another part of the pen becomes detached:
- Stop using the pen.
- Keep the pen, packaging and other components in case they are needed for investigation.
- Contact the pharmacy that supplied it and explain what happened.
- Check that the pharmacy is registered with the GPhC if you bought the medicine online.
- Consider reporting a suspected falsified medicine to the MHRA through the Yellow Card scheme, particularly if you believe the product may not be genuine.
A damaged or faulty pen does not automatically mean that it is counterfeit. However, an unusual device problem is a good reason to stop and have the product checked rather than trying to repair or continue using it.
Our guide to buying genuine Mounjaro explains some of the checks you can make when buying Mounjaro online.
If You Still Cannot Inject
If you have checked the needle, followed the priming instructions and tried to use the pen as described in the manufacturer's instructions, but it still will not work, stop rather than forcing it.
- Contact your pharmacy. The pharmacy that supplied your Mounjaro can advise you about the next steps and may be able to help if the pen appears to be faulty.
- Contact Eli Lilly if you need further help with the device. The relevant UK contact details should be available in your Mounjaro product information.
- Do not take an extra dose to make up for a dose you are unsure about. If you miss or delay an injection because of a pen problem, ask your pharmacist or prescriber what you should do next.
Keep the pen, packaging and any components if you may need to report a problem or return the product.
Until you have received advice, keep the medicine stored according to the instructions supplied with it. Do not use a damaged pen or try to repair it yourself.
Preventing a Stuck Pen Next Time
A few simple habits can make using your Mounjaro pen easier:
- Follow the priming instructions before each injection. Your Instructions for Use explains exactly how to prepare the pen.
- Use a fresh compatible needle every time. Attach it correctly and remove it after the injection.
- Check the pen and medicine before each use. Do not use the pen if it is damaged or the medicine does not look as described in the product information.
- Press the dose knob as instructed. Use a steady movement and do not force it if it will not move normally.
- Store Mounjaro correctly. Unused KwikPens should generally be kept refrigerated at 2°C to 8°C and protected from light. Do not freeze the medicine. Follow the storage instructions for your specific pen, including the instructions for a pen that has been removed from the refrigerator or is in use.
- Do not try to warm the pen artificially. If you have questions about using a refrigerated pen, ask your pharmacist rather than using heat to change its temperature.
If the pen continues to feel stuck or you are unsure whether you have received your full dose, stop and ask your pharmacist or healthcare professional for advice rather than trying to fix the device yourself.
How the Pen Works, Briefly
The Mounjaro KwikPen is a multi dose pen designed to provide four weekly doses. Before each injection, you attach a new compatible pen needle and follow the priming instructions in the manufacturer's leaflet. You then prepare the prescribed dose and press the dose knob to administer the medicine under the skin. The dosing window helps you follow the steps and check the dose.
Once the intended four doses have been used, the pen should be disposed of according to the manufacturer's instructions. Do not try to remove or inject any medicine that remains in the pen.
You do not need to understand how the mechanism inside the pen works to use it correctly. The important things are to follow the Instructions for Use, use a new needle for each injection, prepare the pen as instructed and never force the device.
Key Takeaways
- A Mounjaro pen that feels stuck may have a needle, preparation or device issue. Follow the troubleshooting steps in the Instructions for Use before deciding that the pen is faulty.
- Follow the manufacturer's priming instructions before each injection.
- Press the dose knob as instructed and never force it if it does not move normally.
- A finished pen may contain some medicine, but do not try to extract or use the remaining liquid as an additional dose.
- If the dose knob or another part of the pen becomes detached, stop using it and contact your pharmacy or healthcare professional.
- If the pen still does not work after following the instructions, contact your pharmacy or Eli Lilly for advice. Do not take an additional dose because you are unsure whether the first dose was delivered.
- Your Mounjaro Instructions for Use leaflet is the most important guide for using your specific pen safely.
