The 26-year-old was asked to take his sixth drug test since signing with the team at the end of September after Sunday's game against the Seattle Seahawks. He has now taken five random tests in eight games played, per Marcel Louis-Jacques of the Charlotte Observer.
"This is supposed to be a random system," Reid said Sunday. "It doesn't feel very random."
The player's previous test came on Nov. 8, although he noted that he wasn't worried about the results.
"They're not going to catch me on anything," he said at the time, per Louis-Jacques.
Reid has an active collusion grievance against the league after going unsigned throughout the offseason. The case has continued even after the Panthers signed him.
He was also one of the first players to join Colin Kaepernick in kneeling during the national anthem as a protest against racial injustice, and he continues the protest with Carolina:
There is no evidence these off-field actions have any connection with the drug tests, and Reid will likely remain a starter on the Panthers defense unless he fails one of them.