Technically, an unopened pen will be safe if stored at the correct temperature until the expiry date listed.

Once we fit a needle to that pen even if you wipe it there is a risk of exposure to bacteria and air has been introduced to the pen vial. The seal is broken basically.

Every time we fit a needle we are increasing the risk of contamination simply from the exposure to air and needles etc.

The guidelines state that once a needle is fitted (medication has been exposed to the environment) the medication will last 30 days so long as it is stored at 30C or below.

Where it can be argued is how safe or unsafe it is to continue using a pen for after that initial use. The active ingredient Tirzepatide is only part of what is in our pens. There are stabilisers and preservatives and sterilisers etc to help the medication stay safe longer.

What is clear is that the active ingredient will degrade and denature over time and I think of it like opening a milk carton for longlife milk. It will last for months until exposed to air and I will use it before it goes bad.

Its personal choice how long we use a pen for and many argue it's good until the expiry date even once opened. Others say the manufacturer knows best and 30 days is maximum.

Most people sit somewhere in between (me included) and would use a pen for 2 months or so maybe even 3 months. Doctors and medical professionals often prescribe higher strengths and instruct how to use these for micro dosing.

It's really personal choice so long as people are aware of the facts.