When my son’s blood sugar is low at meal time and he is not given an insulin injection, are the carbs he eats burned as fuel because of the long acting insulin in his system?

The purpose of the long acting insulin is indeed to cover basal energy needs throughout the 24 hours. For many years NPH was the main resource; but more recently Lantus (insulin glargine) has been shown to give very even coverage for nearly the whole day when given without other insulins at bedtime. Basal insulins are not designed to cover the after meal rise in blood sugar when an injection has been omitted. The fact that your son has low blood sugars just before a meal suggests that either he is getting too much NPH or possibly too much Regular insulin at the previous mealtime. Here again the increasing practise is to give one of the new short-acting analogs (Humalog or NovoLog) to cover just the immediate postprandial surge in blood sugar. These insulins can be given right after the meal and adjusted to the pre meal blood sugar and the number of ‘carbs’ actually consumed. If your son is not already on such a regimen like you might talk to his care team about it.

DOB