Quite literally, what’s “normal” depends on who you are. For non-diabetic persons, when looking at “high” numbers, it was long assumed that the body always kept their blood glucose under 100 mg/dL. Now that more and more research is being done on continuous glucose monitoring systems, we see that even non-diabetic folks will sometimes shoot upwards briefly following meals or drinks with heavy carb loads. You know, like when you stop for a 64-ounce Big Gulp, a bag of Doritos, and Ding Dongs on your way home from work (or God forbid, on your way to work). It shouldn’t come as any surprise that a “snack” like this would give even the non-diabetic’s body some trouble.
On the low side, again for non-diabetic folks, being in the high 50s or 60s seems to have no ill effect.
Now if you have diabetes, “normal” is out the window. By definition, having diabetes means normal blood sugar is no longer possible, but the generally accepted target blood glucose levels are around 115 mg/dL fasting with peak excursions after eating at either 150 or 180 mg/dL -- depending on whose standards of care you want to look at. It’s important to note that these “postprandial” targets are based on the assumption of testing two hours after eating. If you test 30 minutes after eating you may very well be above your target.
Numbers below 100 in diabetics make us all nervous because, more often than not, it’s your medication that put you there. So while the non-D body might be comfortable at 50 or 60, a body that has been forced low by meds is not happy there and is in grave risk of going lower. When you are on glucose lowering medications your internal series of checks and balances is gone. Your body may not be able to overcome a med-driven low, which is why the target is kept at 115, to give you a safety zone. It’s never a good idea to skate on thin ice.