Diabetic child, machine reading Hi!?

does child need to go to er if machine reads Hi on home monitor? Blood sugar after hi reading starts to lower to 32mmoh/L after hour and half, and comes down throughout evening but still at 20mmoh/L going to bed (even after fast acting insulin given)What i'm asking is if machine reads hi or even if childs blood sugar reads 32mmoh/L (around 580mg) but caused by what child ate, does child need to go to ER at that hi level?