There are studies out now suggesting that diabetics who get low blood sugar attacks, severe ones, can damage the brain. One severe attack can lead to dementia for them!

Low blood sugars in non-diabetics, but who may be pre-diabetic may not be low enough to affect the brain. I've heard some doctors say it is the DEGREE of drop within a short time that is the most damaging. So dropping suddenly from 200 to 100 is more severe with symptoms than dropping from 100 to 80.

What happens in diabetes is that the high sugar in the blood cannot get into cells. So those cells suffer. Low blood sugar is the same, sugar cannot get into cells if it isn't there in the first place.

When I was having fasting levels of 70, for testing, I could be very cold, twitching in calves, cold sweat, and feeling anxious and sometimes even dizzy.
When my thyroid was fixed, my fasting's went to 90. In fact when I had my GTTs both times I ended up in tears at the end, strung out, and frantic!

This is why having higher good fats in the diet help, and also taking acetyl carnitine to help transport fatty acids into the mitochondria to burn instead of glucose all the time helps too.

I find it amazing that doctors don't understand the biochem and physiology of glucose at all. If they did, they would pay more attention to low readings.