Time: 1990s or early 2000s, not sure
Location: New York City, Alternate Universe, vampires, werewolves, psychics etc. are known, if not normal
The issue: So I've assessed from web searches that the police don't get involved if you fail a drug test, but some other issues have been pointed out below, so here's a summary of what's going on:
Melinda is a journalist with an anxiety disorder (there's a scifi/fantasy twist, but it's probably not relevant to this discussion) and she's been on an effective medication (A) for years. She's investigating some shady dealings between a government agency and a pharmaceutical company. Her informant in the pharma company warns her that if the company learns what she's doing they will find her and inject her with a drug (B) that effectively opens her completely to the power of suggestion--they can tell her to kill herself and she will. The informant gives her an antagonist drug (C) that she has to take every day so that if she's injected with B she'll be able to resist.
The problem is that C also inhibits A from working, so her anxiety starts to return. Her anxiety kills her appetite so she's getting hypoglycemic. To make matters worse, an idiot co-worker, trying to help her lighten up slips some mild sedative (D: possibly a small amount of ketamine) into her coffee. The feelings brought on by D make her think she's been drugged with B, so she takes a double dose of C, which completely counteracts A and causes her to have something like a PTSD episode.
Disoriented she claims she's been poisoned before passing out (from low blood sugar) and that's why she's taken to the hospital. When she comes to, she is terrified of the doctors (major plot point later, related to the PTSD thing) and runs away.
So, would hospitalization and a drug test be warranted by her claims of beign poisoned and behavior? The fainting is really irrelevant, I just needed her to be brought in unconscious. I went with PCP as a false positive from ketamine because it seemed to explain her behavior as well as some chest pains she was having (I read PCP can cause sudden heart failure days after a single use).
Does any of this make any sense? My knowledge of medicine is limited to TV shows and there are too many factors here to search for.