Lows are cause by excess insulin, somewhere in the equation. Whether absorbed too rapidly, too little food to make energy required, excess exertion, somewhere its excess is the reason for any low, yes?Well, yes... but sometimes no... the best answer actually is, sort of.
And that's honestly the best, most accurate and medically scientific answer that can be given.
Clearing glucose from the blood is much, much more complicated than a simple linear, strict relationship between quantity of glucose in the blood, and quantity of insulin.
The simplest way to see this is to be female, and observe how one's sensitivity is different depending on hormone surges and variations during the menstrual cycle.
We all see this variability when sick vs. when not. Also, stress, anxiety, etc. mess with the potency of insulin through a variety of hormones, chief among them cortisol and adrenalin.
Bottom line is that eating exactly the same meal, to the gram, and taking the exact same insulin dose, can result in a hypo one day, and never returning to target the next, requiring more insulin as a correction.
So, the simplicity that you assume that would result in the risks you're stating just isn't the case. As such, control has a fair bit of "art" to it, whether tight or not, if you're striving for "normal" BG levels as your target. In fact, such a predictable, reliable relationship as you assume would be a Godsend to us tight controllers -- we'd never have hypos, ever. We'd be very measured and precise about what we eat (we're tight-controlling, remember), take exactly the precise insulin to cover it, and voila! We would wind up right back where we started before the meal, never going too low.
