Restarting MJ with used pen?

[MJFEB2026]

I started mounjaro in February. Took 4 x doses of the 2.5mg pen. Moved up to the 5mg pen, took one dose first week of March and got ill (with something unrelated to the MJ) and had to stop dieting.

The pen has been stored in a drawer and still has 3 doses left in it. When I start up again (in a couple of weeks) can I use this pen or should I start again on 2.5mg?

I'm very lax with MJ but as the pen hasn't been stored in the fridge, and has had a dose taken from it, even I would throw it away.

Also - yes, you need to start again on 2.5mg.

If your 5mg pen had been in the fridge, I'd have suggested that you use it to get your 2.5mg doses out ( 0.3ml or 30 clicks).

It's been open for up to a month longer than the 30 day expiry so far, depending on when you used it in March, so up to 6 weeks or so past expiry if you use it a few weeks from now. It also hasn't been kept in the fridge.

I wouldn't choose to use this pen. It's likely degraded to some extent plus the possibility of bacterial contamination. Probably other people will have a different attitude to risk and be happy to use it.

Thanks both. I will throw it away.

Do the pens have to be stored in the fridge once opened?

No they don't, they can be at room temp (>2 degrees and < 30 degrees) for their 30 day usage time. But, if you plan to use a pen longer than 30 days and disregard the 30 day usage guideline, then keeping it in the fridge will reduce the risk of bacterial growth and degradation.

I see! Thank you!

I’d use it if it’s been in a fridge - although half doses - even if open but if it’s been in a drawer need to bin after 30 days.