it would have been better if you had mentioned the age of your friend..
coming to your first issue about having taken vyvanse
, it is a stimulant so there will be an association with low sugar levels and stimulant drug cause it leads to faster usage of calories..
also the fact that this drug has dependency issue there is always a chance to abuse it hence not advisable to use it for night outs and study periods..
since he is on pump therapy as you say.. there is no issues with adjusting insulin
the pump measures the sugar levels and calculations are adjusted for insulin release..
he will be able to recognize when sugar is low with shaking hands(tremors) , tachycardia
( fast heart rate
), palpitations ( aware of one's heart beat) excessive sweating
, dis orientation etc..