# Insulin Math

I use Humalog U-100. The vial is supposed to contain 1,000 units in it. My pump reservoir holds up to 300 units at a time. That means I should be able to get 3 full reservoirs (3x300=900) plus another 100 units in a fourth.
So why is it that I can only get 2 full reservoirs (2x300=600) plus another 150 units in my third before the vial is completely empty.
Obvious questions you might have are:
The reservoir goes a bit over 300, are you sure you don’t go over that? Yes, I’m sure.
The vial might look empty but still have some insulin in it, are you sure it’s completely empty? Yes, positive.

I’d say that it’s my poor math skill, but it says it very clearly on the vial that it contains 1000 units and while my math skills might be less than stellar I can count from 1 to 3 (meaning I know I’m not forgetting a filled reservoir in between and only think I filled 2 full when in fact I filled 3).
Any ideas.

that sounds really weird… ponders can’t think of anything ex. maybe they lied to you about how much it can contain…

Well one thing is you lose about 20 units in the tubing. It does not account for it all, but i usually figure three vials uses 60 units. Then I knwo I waste at least another 30-40 because of leakage after I press the air into the vial in order to help the insulin come out. Otherwise, I figure Lilly is messing with us?

rick phillips

Same here…then when I set the pump up to finish the prime, I have only about ~160 still in the reservoir.

I usually can pull 3 reserviors and pull around 50-80 out into the 4th. But im really anal about not wasting any insulin

300u means 300u available to use, not how much it actually contains… when I had my 5xx paradigms I’d get 5 cartridges out each vial… with zero left over… so there was 24u being “lost” with each of those… and I only filled them to the line…