My daughter usually goes to bed with a blood sugar reading of around 90 mg/dl [5.0 mmol/L]. We were recently told her “goal” should be 120 to 150 mg/dl [6.7 to 8.3 mmol/L]. When she was first diagnosed, her range was 80 to 150 mg/dl [4.4 to 8.3 mmol/L]. With the 90 mg/dl [5.0 mmol/L], she doesn’t have any symptoms, but we read that when your blood sugar is below 120 mg/dl [6.7 mmol/L], it affects you mentally. So, what is the low blood sugar level that is considered dangerous?

This is an oversimplification as you state. Normal blood glucose values are in the 60 to 90 mg/dl [3.3 to 5.0 mmol/L] range before eating and overnight and go up to about 126 to 140 mg/dl [7.0 to 7.8 mmol/L] after eating. So, one therapy goal is to approach normal. This turns out to be extremely difficult since our treatment is not as good as the natural pancreas function. So, we must make allowances for these approximations. However, if you are not having problems with bedtime blood glucose levels around 90 mg/dl [5.0 mmol/L] and you have checked overnight blood glucose values and also check pre-breakfast values, then I’m not so sure that you need to modify anything. However, if there are recurrent problems with nocturnal or pre-breakfast hypoglycemia, then it would be prudent to have slightly higher bedtime and overnight targets to try to avoid these. I would encourage you to go back and discuss this in more specific detail with your diabetes team so that your child’s target blood glucose values can be individualized rather than generalized.

SB