What determines if a drug is swollowed, smoked, shot up or whatever?

Question

What determines if a drug is swollowed, smoked, shot up or whatever?

Answer 1

It's usually determined by blood, urine and hair samples taken from a user and taken to a lab to be analyzed, or it can easily be seen depending on the method used by the user like needle the tracks on arms, dilation of pupils and a runny nose w/ a powdery substance at tip of the users nose if they have sniffed or shot up.

Answer 2

the user of the drug.