How do you know insulin is working?

Or that you're taking enough?

I've only used it twice post-workout thus far, 4 and 6 iu respectively. I realize I'll probably have to get up to around 10 iu to notice it's true effect. And I know it's still early, but what do you look for? Signs of feeling fuller? Better pumps? Weight gains? How do you know you're taking enough?

good pumps, muscles look fuller.