That happened to both my kids,  after an overnight-  they were both a little sick though.  It can be too long for them to go without food or drink.  When my kids get sick now,  I wake them up in middle of the night and redose and give a sweet drink.

Dr. Merke at NIH does provide glucose monitors to some of her patients,  so I know if can be a concern. You may want to contact NIH if you do not get a clear answer from your endo. 

Good luck.

My boys are both SW CAH and it happened between the ages of 2 and 4,  they are now 8 and 11.