The joy of starting a new vial

I use vials and kwik pens for insulin drlivery. Has anyone else ever notice that when you start to get low on a vial it’s like the insulin doesn’t seem to work as great anymore. But when you start a fresh vial or pen, it works fabulous and you get wonderful BS numbers.

I try to mark down when I start a new pen and toss it when it starts getting weak. I like using pens because I don't throw as much away as I do with vials.