[zaroth]

T1D patients use both types if they are self-injecting. The long acting covers your basal rate (baseline) and the fast acting covers carbs you eat.

Or if you have a pod or pump then you can use only the rapid acting and the software will drip it slowly to cover your basal need over the 24h.

Trying to use just the fast acting with self-injections doesn’t work because you go high overnight while you’re sleeping, and even during the day you would have to be injecting every 3 hours to keep up. (E.g. when your pump controller dies on vacation and all you have on hand is rapid-acting)

Source: I have two kids with T1D.

[basch]

Which would be covered by traditional mixed, short and intermediate insulin, right? The price of Novolin 70/30 (mixed), Novolin R (rapid) and Novolin N (intermediate) insulin have remained flat since 2014. (Short acting and Rapid are two different things, the former being the old kind of insulin that takes 30 minutes, the latter being modern tech that takes minutes.)

It's when you want something better, that lasts longer than Novolin N that price starts to go up. (Novolin N is typically injected underneath the skin (subcutaneously) once or twice per day.)

Obviously, if you have insurance, I would expect you to be being prescribed something better, because that's how the world works. Then you can jump from traditional insulin to rapid and long lasting, and pens.