A little update on this. I mixed the expired glucagon 5 days ago. It worked fine then. I tested it a day later, and it still worked.
So 5 days after mixing the glucagon, I did another test today. The same mini-dose I did before, 25 units (just 1/4 of the entire dosage you get in a glucagon kit), and it brought me up 89 points in just 30 minutes. That’s pretty consistent with day 2:
2nd day after mixing:
106 points in 35 minutes
5th day after mixing:
89 points in 30 minutes
Anyway, the point is, glucagon doesn’t seem to expire when the label says, and it works even up to 5 days after mixing. Maybe longer. I have a little left, I will try again in a few days…
Funny to see, no doubt that 5 day old mixture is working: 
