Reid reacted with consternation when he was tabbed for a drug test after Thursday's loss to the Pittsburgh Steelers, saying it was "like the fifth time since I've been here" that he'd been chosen for a random test.
Reid signed with Carolina in September and has played six games with the team. He returned to the league saying he would continue to kneel during the national anthem to protest social and racial injustice in America.
NFL spokesman Brian McCarthy took to Twitter on Friday to reassert that the drug testing process was random, repudiating suggestions that Reid was being targeted.
"Re: PED testing: Each week during the season, 10 players per club will be tested. By means of a computer program, the policy's jointly appointed Independent Administrator randomly selects before the game players to be tested," McCarthy wrote, providing a link to the league's performance-enhancing drug policy.
Thursday's demand for a post-game drug test came after Reid was ejected from the contest in the third quarter for a head-first hit to sliding Steelers quarterback Ben Roethlisberger.
"I didn't even know you could be ejected," Reid said. "The referees told me I was targeting him, which I disagree with."
Panthers coach Ron Rivera agreed the hit -- on which Reid's shoulder hit Roethlisberger's head -- properly drew a penalty, but he thought the decision to eject Reid was wrong.
"I don't think that was warranted, I really don't," Rivera said. "I don't think he hit him hard enough to eject him."