How to spot LSD usage?

[PoBoy321]

This is probably a good place for you to start looking. Also, my understanding is that LSD is a fairly difficult drug to tell if someone uses on a regular basis if they aren't high. When they are high, besides the obvious stuff (talking about the walls melting), a telltale sign is enlarged pupils.

In your shoes, I would just bring it up to the friend, making sure to clarify that I was asking as a friend and not as an employer.