M41, diagnosed T1D (LADA) in May 7 months ago, still surfing my honeymoon (hopefully).
I have 2 pens, glargine and aspart, first used about 4 months ago. Keeping them on a cabinet next to bed, room temperature (17-20C), in a thermo-protected travel pouch.
About a week ago I noticed that I need mor
Not a doctor and no scientific proof of anything but I leave my insulin in my work truck here in South Texas. Cab temps get up over 100°. I have not noticed any change in efficacy. I even use “old” insulin that’s been out of the fridge for way longer than 28 or 30 days (whatever that magic number is). Like, almost a year out of the fridge. Works the same as when it was fresh from the pharmacy.
Insulin has a shelf life, 28 days for most insulin once it is opened. 4 months ago definitely exceed that time frame. Some insulins can last longer (42 days for Novolin-N) and I believe the Wiki has these documented for lots of different insulin. Glucose Meters, Insulin, Pumps
On top of that heat does break down insulin, as does freezing. Insulin can handle a little heat, like carried around in the summer heat for short periods is fine. Left sitting in a hot or frozen car is not fine.
My very first pen was a demo pen my endo used, with the use before date of 08.2025 - I used it all the way through the end of August, so it was waaay beyond the 28 days, and all worked 🤷
Heat can definitely be an issue.
The rapid-acting insulin analogs (lispro and aspart, i.e., Humalog, Novolog and Fiasp) are a lot more sensitive to heat than Regular insulin (and NPH and Ultralente, which are combinations of Regular and other chemicals). Not sure about the glargine (generic Lantus).
Rapid-acting insulin should be kept refrigerated until you open the vial (or start using the pen), and then it's often better to keep it at room temperature because constantly shifting from room temperature to refrigerated and back can actually be worse for it. Regardless, it's supposed to be used within 28 days of taking it out of the fridge.
Rapid-acting insulin will usually act more slowly (more like Regular) long before it becomes completely useless.
Hmm.. gonna read up a bit about the variations. But it looks like the main issue is somewhere else then
Hard to tell