Mounjaro 5th Dose: Is It Safe?

If you’re using Mounjaro for weight loss or diabetes, you might have heard about the “fifth dose” that some users try to get from their Mounjaro pen. But is this safe? What should you do if there’s liquid left in the pen after your prescribed doses? In this article, we’ll explain what the extra “fifth dose” is, whether it’s normal to have liquid left over in your pen and why using this leftover liquid could pose risks. We’ll also guide you on the best practices for handling any leftover medication to ensure your treatment stays effective and safe.

Key Takeaways

Here are the 5 biggest takeaways from this article about the Mounjaro 5th dose:

• The leftover liquid in the Mounjaro pen is a buffer, not a complete or reliable dose. The pen is designed to provide exactly four doses of medication, and the extra liquid is included to ensure consistent delivery of those doses.

• It is completely normal to see liquid remaining in the pen after using all four doses. The buffer is an intentional part of the pen's design to account for small variances and ensure that each dose is delivered accurately.

• Attempting to use the leftover liquid as a "fifth dose" can lead to inaccurate dosing, resulting in underdosing (which may reduce effectiveness) or overdosing (which increases the risk of side effects such as nausea, vomiting, or diarrhoea).

• After administering the four doses, the pen should be discarded in a sharps disposal container, even if liquid remains. Do not attempt to extract or inject the leftover liquid.

• If you have concerns about dosing, side effects, or how to dispose of the pen, consult your doctor or pharmacist.

What is the extra "fifth dose" of Mounjaro?

The “fifth dose” of Mounjaro refers to the extra liquid that some users notice is left in their pen after taking their prescribed four doses. A Mounjaro KwikPen is designed to deliver four doses of medication. People may notice liquid remaining in the pen after taking their 4 doses as they typically come with a buffer of extra liquid. This buffer is intentional to ensure consistent delivery of the four prescribed doses. Whilst it may look like a fifth dose, the leftover liquid is not a complete dose and should not be used.

If you have any questions about Mounjaro dosage or titration then you should consult with your doctor for advice. Titration refers to the changes in dosage as you progress with your medication. We have previously discussed Mounjaro dosing and titration to help you understand this process [1].

Is it normal to have liquid left in my Mounjaro pen?

Yes, it is completely normal to have liquid left over in your Mounjaro pen after you have used your four doses. The leftover liquid is known as a buffer and is an intentional part of the pen’s design [2]. The buffer is intentionally provided in the pen to ensure that the four doses can be fully administered. It means that even if a small amount of liquid is lost the full dose will still be delivered.  

Should I use the fifth dose?

No, you should not use the fifth dose from your Mounjaro pen. While it may seem tempting to use the leftover liquid, it is not a measured or reliable dose. The buffer liquid included in the pen is designed to ensure the proper delivery of the prescribed four doses, but it is not formulated to be an additional dose. Using it could result in receiving too much or too little medication, both of which carry risks.

An underdose may reduce the effectiveness of the treatment, while an overdose increases the likelihood of side effects such as nausea, vomiting, diarrhoea or constipation. These side effects are more likely when your body hasn’t had time to adjust to the medication, which is why Mounjaro’s dosing schedule starts low and gradually increases (titration).

Following the recommended dosage instructions ensures your treatment is safe and effective, helping you achieve the best possible results with Mounjaro.

What should I do with the liquid left in a Mounjaro pen?

If you have liquid left over in your Mounjaro pen after you have used your four doses then you must dispose of your pen properly. If you are unsure about how to properly dispose of your pen then it is important to consult with your doctor or a pharmacist for advice. You should not attempt to get the remaining liquid out of the pen and you should not inject the liquid as a fifth dose.

Medically Reviewed by:
Dr. Alexis Missick MBChB. MRCGP
GMC Reference no: 7151419
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Sources

[1] Mounjaro dosing & titration: Which tirzepatide dosage do I need? - UK Meds

[2] What excipients does the Mounjaro® (tirzepatide) KwikPen® contain? - Lilly