The 10 - 40 uIU/mL on the Cornell lab report got me too. Ive been doing a lot of reading in the files and here is what ive gathered so far: turns out tge Cornell range (reference interval) is a reference range not a normal range (although it looks like one the way it's used in the report). You can search "VA Tech pony proxies" in the files and you will get info on what a normal range should look like, i.e. less than 10-12 uIU/mL. From what i have read in the files, the lab reference range or interval Cornell cites includes all sorts of testing conditions that can increase insulin , such as: recent exercise before blood draw, recent high sugar and/ or starch meal, sudden cold temps, stress, etc. I'm sure there are lots of other factors more knowledgeable peeps can fill you in on. The VA Tech pony study established a safe insulin range for both previously laminitic and non-laminitic ponies to keep them from slipping into endocrinopathic laminitis triggered by high insulin (i think i read somehere where Dr. K said that 80 uIU/mL was the tipping point there, but we'll see if someone else can give us confirmation on that. The thing about the Cornell lab reference range is that it doesnt use any proxies to determine normal. Their numbers are not adjusted to compensate for various feed/exercise etc. scenarios at the time of testing (and im not sure how one could normalize that kind of uncontrolled data anyway since there arent any standard calculations to adjust insulin results from all the various feeding and exercise states of the horses they tested. The pony proxies, on the other hand, provide a normal range when testing occurs in a fairly controlled and repeatable way--blood draw 4 to 6 hours after 1st meal of the day and horse steadily eating hay the whole time right up to blood draw.
I hope that helps and that someone will jump in if I've misstated anything.
Amy & Princess (12 year old KY Mtn Saddle mare) & Max (6 year old mini gelding) - both PPID/IR
Southeast TN, Joined 2019