
Quoting
Mr. Knowitall
You can contact your probation officer before you fill a prescription, and certainly before you start taking pills. A probation officer can be reasonably expected to distinguish between medication administered in an emergency room setting, where there is no reasonable opportunity to provide notice, and that taken at a later time after filling a prescription.
This is even more of an issue if there is a history of substance abuse, which is presumably why the testing was ordered, and even moreso if it's opiate or pain pill abuse.
Definitely take the prescription and pills with you, so you can prove that you took them only as prescribed.