Timesulin Is a Smart Timer That Fits Onto Your Insulin Pen Timesulin is a replacement cap for insulin pens with a built-in timer that helps ease the daily anxiety and frustration that millions of people living with diabetes feel when trying to remember whether or not they've taken their insulin injection. in Public bookmarkswith diabetesinsulin_pentimesulin Note: Timesulin is a replacement cap for insulin pens with a built-in timer that helps ease the daily anxiety and frustration that millions of people living with diabetes feel when trying to remember whether or not they've taken their insulin injection.