We are both diabetic and yesterday both of us really messed up our insulin dose. She ended up with a 68 which is bad for her and I ended up with a 43. (80-150 mg/dl) is the target. It will take me a day or so to recover from the swings (43 to 300). It's a really nasty juggling act. I'm insulin resistant ans she is insulin sensitive. Man made insulins have a lower response time which contributes to the control issue. As you have more low attacks, they become harder to "feel". I do "wake up", so far, if I have a low during sleep.
Real time glucose monitoring systems exist, but the insurance creiteria is hard to meet.