ask him if he/she has anything left!lol! seriously though...it would depend on how serious you thought the situation was..for instance i know lots of people who take drugs..some are recreational users and some i've had to speak to as i thought that it was becoming a bit of a problem. whatever way you approach it ,you risk being unpopular as when someone has a problem with drugs or alcohol..they are the last one to see it as such. tread carefully would be my advice!