Is it necessary to test a child's blood sugar during the night if he has juvenile diabetes and is on insulin?

At least at bedtime. Mostly, we just ask parents to test blood sugars before bedtime. However, nocturnal hypoglycemia is both common and potentially dangerous. If there are any concerns for overnight lows, middle of the night blood sugar checks are helpful. Likewise, if your child is sick or goes to bed high, checking a blood sugar overnight is also helpful.