You only get flagged as a drug seeker for drug-seeking behavior.

Exactly. My wife and I take a mix of Sudafed & another medicine when we have bad colds. The active ingredient for them is pseudoephedrine which can be used to make meth, so our state requires ID and limits how much you can purchase a month. On more than one occasion we’ve purchased the maximum we could in order to stock up before cold & flu season. Never had any issues doing so.