If you have finished a Mounjaro injection and are worried because some liquid seemed to leak, the needle did not really pinch, or there is still liquid left in the pen, there is usually no reason to assume that your dose was missed based on these signs alone. The UK product information states that each KwikPen contains four doses of 0.6 mL and that any excess solution remaining after use should be discarded. If you use a Mounjaro pen and want to know whether your dose was delivered, the key is whether you followed the injection steps correctly and held the pen in place for the time stated in the Instructions for Use.
This guide explains how to check that you followed the Mounjaro injection procedure correctly, what leaking or barely feeling the injection may mean, what a finished pen can look like, how to use the pen correctly, and why you should never try to take another dose or take an additional dose from the leftover medicine in the pen. It is easy to worry when you see liquid remaining or feel very little during an injection, but these signs alone do not confirm that your dose was missed.
First, the Reassurance
Two things are worth knowing straight away. Seeing some liquid left in the pen after the prescribed doses does not necessarily mean that anything went wrong. The UK product information states that each KwikPen contains four doses that can be administered and that any excess solution remaining after use should be discarded.
Also, not feeling much during the injection does not by itself mean that the medicine was not delivered. The needle is very fine, so some people may feel only a small amount of discomfort or very little at all.
The sections below explain what to look for instead.
"The Needle Did Not Pinch Me", Does That Mean It Failed?
Not necessarily. You may feel only a small amount of discomfort, or sometimes very little, during an injection. Not feeling much does not by itself mean that the medicine was not delivered.
Follow the injection instructions supplied with your KwikPen rather than using pain or sensation to judge whether the dose was delivered. What matters is whether you completed the injection steps correctly, including holding the pen in place for the time stated in the Instructions for Use.
How to Tell If Your Injection Was Completed Correctly
The best way to check that you followed the injection procedure is to use the Instructions for Use supplied with your pen. This includes pressing the dose knob as instructed and holding the pen in place for the stated amount of time before removing it.
Do not use the sound of clicks, the amount of pain, or the amount of liquid you can see in the pen to decide whether your dose was delivered. The clicks you hear while preparing the pen are part of the pen's operation and are not, by themselves, a sign that your injection is complete.
If you are unsure whether you completed the injection correctly, speak to your pharmacist or prescriber rather than taking another dose.
"Liquid Spilled" or Leaked, What Does It Mean?
If you notice a small amount of liquid at the injection site after removing the needle, this does not necessarily mean that you missed your dose. A small amount of liquid on the skin can be difficult to judge, so you should not try to estimate how much medicine was delivered from this alone.
If you think a significant amount of medicine leaked out, the injection was interrupted, or you are unsure whether the full dose was delivered, contact your prescriber or pharmacist for advice. Do not take another dose to try to make up for it unless a healthcare professional tells you to do so.
Follow the injection technique described in your Instructions for Use, including the specified holding time, rather than trying to correct the situation yourself.
If You Think You Missed Part of a Dose
This is an important medicine safety point. If you are not sure that your full dose went in, do not inject again to "top up". Do not use the leftover liquid in the pen, and do not add it to your next dose.
The UK product information states that each KwikPen contains four doses of 0.6 mL and that any excess solution remaining after use should be discarded. The remaining solution should not be used to make up a dose.
Instead, contact your prescriber or pharmacy and explain what happened. They can advise you on what to do next based on your circumstances.
What Does a Finished Mounjaro Pen Look Like?
This is where a lot of confusion starts. A finished pen may still have some liquid inside. The Mounjaro KwikPen contains four doses of 0.6 mL that can be administered, and the UK product information states that excess solution may remain after use and should be discarded.
Because some liquid can remain, you cannot reliably tell whether a pen is finished by looking at the liquid level. The markings on the cartridge are also not intended to show how many doses remain.
The way to know is to count your doses, not to judge the liquid level:
- The pen should be discarded after four weekly doses.
- A pen in use should also be discarded after 30 days after first use, even if you have not used all four doses.
Keeping a note of your injection dates can help you keep track of which dose you are on.
"One Dose Left", How to Know
The same rule applies. Work out how many doses remain by counting the injections you have taken, rather than looking at the liquid in the pen.
If you have administered three weekly doses from a pen, one scheduled dose remains. After the fourth dose has been administered, you should not take another dose from that pen, even if some solution remains.
The UK product information states that any excess solution remaining after use should be discarded.
Can You Use the Liquid Left in the Pen?
No. Any solution remaining after the four doses have been administered should not be treated as an additional dose. The UK product information states that any excess solution remaining in the pen after use should be discarded.
The pen is not designed to provide another complete dose from the remaining solution. Do not attempt to withdraw the remaining medicine with a syringe or otherwise extract it from the pen.
Doing this would be outside the manufacturer's instructions and could result in an amount of medicine being given that has not been measured or prescribed.
The leftover solution should be discarded with the pen according to the disposal instructions provided with your medicine.
What If It Is Wegovy, Not Mounjaro?
If your medicine is Wegovy rather than Mounjaro, do not assume that exactly the same instructions apply. Wegovy uses a different pen and has its own Instructions for Use.
Follow the instructions supplied with your specific product. If you are unsure how your pen works or whether your dose was delivered correctly, speak to your pharmacist or prescriber.
When to Contact Your Prescriber or Pharmacy
Contact your prescriber or pharmacist if:
- The solution appears cloudy, discoloured or contains particles.
- The pen appears damaged or is leaking.
- You are unsure whether you received your prescribed dose.
- The injection was interrupted or you think a significant amount of medicine leaked out.
The UK product information states that the solution should be clear and colourless to slightly yellow. It should not be used if particulate matter or discolouration is observed.
Because Mounjaro may be prescribed for weight management, any uncertainty about your dose should be discussed with a healthcare professional rather than corrected by taking more medicine yourself.
If you suspect a problem with the medicine or pen, speak to your doctor, pharmacist or prescriber. Suspected problems with medicines or medical devices can also be reported through the MHRA Yellow Card Scheme.