Like "Almost universally a good blood sugar is good for everyone. How you actually feel with that blood sugar is different though. If your body is used to higher blood sugars then it will throw symptoms of hypoglycemia at blood sugars that it shouldn't. It can also happen if your blood sugar drops at a fast rate. Within a weeks or so of having lower blood sugars your body will adjust back to where it should be but if you have large, fast drops in blood sugar you may still get symptoms. It's a double edged sword, especially for insulin users, because if you have too many low blood sugars your body will think of them as normal and won't throw symptoms until you are dangerously low."