Mounjaro Pen FAQs: Jams, Leaks & Air Bubbles Explained
13 March, 2026 | Holy Winter - Healthcare Writer
Using injectable medications like Mounjaro (tirzepatide) can be a real game-changer when it comes to your weight loss journey and an overall healthy lifestyle, but sometimes, small issues - such as air bubbles and/or jams - can get in the way of safely medicating and, inevitably, cause stress.
Today, the healthcare professionals at iQ Doctor look at troubleshooting semi-common issues with Mounajaro self-administer pens. Knowing the key signs of problems (and how to fix them) can save you time and money, as well as mitigating frustration.
Before Starting Weight Loss Medication: Handle Your Mounjaro Pen with Care
Just should always start by thoroughly washing your hands (as well as the injection area) and ensure that you are working in a well-lit location so you can administer your dosage safely and cleanly.
Your Mounjaro pen is a delicate medical device containing a fine surgical needle. Never try to take apart, deconstruct or brute force and mechanism on the pen, as this could damage the device and adversely affect your weight loss treatment.
Mounjaro Pen Not Working as Expected?
If your Mounjaro pen isn’t working properly, it could simply be as a result of there being slightly too much pressure inside the cartridge, which may cause the pen to jam or be more difficult to use.
Don’t worry - this is an easy fix - and is not a manufacturing fault. You may notice:
- The dose knob won’t press completely
- The knob doesn’t make the usual clicking sound when you turn it
- It’s hard to turn the dial, or it won’t turn at all
Here are some causes and solutions for common Mounjaro pen difficulties:
Mounjaro Pen Needle: Blocked or Bent?
If the pen isn’t injecting properly or the needle appears bent or damaged, it is best practice to be safe and replace it with an entirely new one.
Before each use, check that the needle is straight, firmly attached, and that both the inner and outer needle caps have been completely removed. A bent, loose, or blocked needle can stop the medication from flowing correctly, meaning you may not get your entire dose.
Is Your Mounjaro Pen Leaking?
Always ensure the needle is completely attached before priming or injecting.
Priming without a needle can cause too much pressure to be stuck inside the cartridge, which may cause the red rubber seal to push and cause leakage.
The “Golden Dose” of Mounjaro
Sometimes, you may see a small amount of liquid left in the pen which looks similar to a dose, but is actually the “priming dose” or “golden dose”, left by the manufacturer: it is important not to confuse this with a full dose.
Keeping an injection diary can help you track your weight loss doses accurately.
Proper Mounjaro Pen Storage
Store your Mounjaro pen in a clean, dry place.
Always remove the needle before storing to prevent leaks, blockages, or air from getting into the pen. Make sure the pen cap is securely attached when the pen is not in use.
If the dose knob becomes hard to press, it could be due to dust, dirt, food, or liquids getting inside. If this happens, it’s safest to dispose of the pen and use a new one.
How Can Mounjaro Pen Issues Be Avoided?
Even if you’re experienced in using Mounjaro pens, small mistakes can cause big issues. Here’s how to avoid commonly occurring problems:
- Always prime your pen before injecting to ensure the medicine flows correctly.
- Use a new needle each time, to prevent blockages and infections.
- Check that the needle is straight and securely attached before every use of your Mounjaro pen.
- Never press the dose knob without a needle attached to the main device—this can increase pressure and cause the pen to jam.
- Inject slowly, counting to five after pressing the dose knob to ensure you get the full amount of weight loss medication.
- Always ensure that your pen is clean and dry, whilst also avoiding letting dust or liquids inside.
Air Bubbles in Your Mounjaro Pen
It’s normal to see small air bubbles inside your pen, especially near the end of a cartridge. While these bubbles usually aren’t harmful, they can make dosing less accurate.
Is It Safe to Use a Mounjaro Pen with Air Bubbles?
Yes! As long as you prime the pen properly before injecting, which will allow these to be pushed out, it’s generally safe to use even if there are small bubbles inside. Priming clears the air so you only inject the Mounjaro medication.
How to Prime Your Mounjaro Pen and Remove Air Bubbles
Before each injection, turn the dose selector to 0.5 mg (or the smallest dose) and press the button until a drop of medicine appears at the needle tip. This pushes air out and ensures your dose is accurate.
If you see bubbles inside the pen, gently tap the side to move them toward the needle, then prime the pen again before injecting.
How Do I Fix a Stiff Plunger on a Mounjaro Weight Loss Pen?
If your Mounjaro pen has a plunger that feels stiff, there are a few simple steps you can follow to ensure a smoother injection experience.
First, make sure to fully remove the pen from your skin before troubleshooting. Replace the needle with a new one and properly prime the pen to ensure it’s ready for use.
When you're ready to inject, hold the pen at a 90-degree angle against your skin. Place your thumb firmly on the injection button and press with steady, moderate pressure until you hear a click—this sound indicates that the dose has been delivered.
To ensure the full dose is absorbed, keep the pen pressed against your skin and slowly count to five before removing it. These steps can help reduce resistance and make the Mounjaro injection process more comfortable and effective.
Be sure to follow these instructions if your come across difficulty using your mounjaro pen, whether or not you purchased it from iQ Doctor. Being committed to and reaching weight loss goals can already be frustrating and full of challenges, so mitigating difficulty elsewhere is useful.
Always remember that, when utilising GLP-1 weight loss medication, it is advisable to incorporate healthy habits such as burning more calories through increased physical activity, reducing portion size and consuming an overall reduced calorie diet. Weight loss medications, such as wegovy and mounjaro, contribute to weight loss in tandem with other positive changes to reduce body mass index (BMI) and, ideally, mitigate weight related health conditions and other side effects of obesity including poor general cardiovascular health.
iQ Doctor is a registered UK pharmacy that specialises in medical remedies for weight loss (including Wegovy and Mounjaro ), erectile dysfunction , hair loss support and much more. Whether you require over-the-counter relief, or prescription-only medication, the experts at iQ Doctor can assist. Please get in touch if you need any further advice.Starting treatment with iQ Doctor couldn’t be more straightforward, simply set up an appointment with a member of our specialist weight management service team of healthcare professionals and start today.
Also, be sure to keep in touch with iQ Doctor via our social media channels as well as keeping up to date with us by signing up to the mailing list.
Reviewed By
Omar El-Gohary
The superintendent and lead pharmacist - registration number 2059792.
Omar is passionate about developing healthcare technology to empower our patients.