heroin is he using or not?

my friend has come ot of jail of a three year sentance an tells me he no longer uses heroin,i am worried .his pupils are narrow like dots he complains about dizzyness an head aches are there any sure symptoms to look for that might help me be sure short of asking him?

I have never seen those narrow dotlike pupils on someone who does not use heroin.

after being on heroin for ten years i can say definatly yes