Jay Cutler was dropping back and firing passes, just as he plans to do on Sunday.
He said doctors "wanted to make completely sure" he was ready before clearing him Monday. He's among several players who have sat out with a concussion, including fellow quarterbacks Kevin Kolb and Matt Moore.
Green Bay's Aaron Rodgers might join the list after absorbing a helmet-to-helmet hit late in Sunday's overtime loss at Washington.
Cutler practiced on a limited basis last week after being sacked nine times in the first half of a loss to the New York Giants.
The Bears (4-1) beat Carolina last weekend, even though backup Todd Collins threw four interceptions before getting benched for Caleb Hanie.
"It's tough," Cutler said Wednesday. "This league is all about battling through injuries. But obviously, concussions and your head is something you have to take pretty seriously."
He said he felt good enough to play against Carolina, but extra caution was taken.
"Concussions are kind of tricky," Cutler said. "You're never really for sure when you're 100 percent healthy. ... Everyone thought it would be better if I waited another week."
Cutler experienced "dizziness" and "general fogginess" and missed his first start due to injury. He had made 57 in a row since Denver turned to him as a rookie in 2006, before a beating against the Giants stopped that streak.
It also wiped out much of the goodwill the Bears had created during a 3-0 start.
Coach Lovie Smith had said the Bears started noticing symptoms after the second-to-last play of the second quarter in that game, when Cutler's head banged the turf while being taken down by Aaron Ross on the Giants' ninth sack.
Cutler, who said the concussion was his first, wasn't sure when the injury occurred. He had taken several big hits before Ross' sack and acknowledged, "There were some moments in the second quarter where I wasn't completely aware of what was going on."
Cutler got up and took a few steps toward the wrong sideline before correcting himself.
Soon after, he had what appeared to be a dazed look when the TV cameras showed him sitting on the sideline, and his decision-making was questionable.
Cutler held onto the ball too long at times, with most of those sacks coming on four-man rushes, and Collins was behind center when the second half started.
"We just had some breakdowns," he said.
Cutler said he could have avoided some of the sacks, although his wooziness played a role.
"I don't think it helped," he said. "But I think I still knew what was going on. I still knew what the hot reads were, still knew where guys were at in the field."
Cutler said the concussion had no effect on his diabetes and he doesn't anticipate seeing the doctors again before Sunday's game.
"It's tough," he said. "You think you feel OK. It's just so hard with your brain. Those second concussions are the ones that are a little tricky."
It would help if he had better protection — a big issue the past few seasons.
The Bears have used three different lineups on the offensive line because of injuries and poor execution, and will be juggling the rotation again with Chris Williams (hamstring) returning and Roberto Garza (knee) now sidelined.
Garza is set to have arthroscopic surgery and will miss the Seattle game. Williams is back after missing the last three and there's no guarantee he'll be back at left tackle.
Offensive coordinator Mike Martz indicated he could be moved inside, saying, "He's natural inside because he's so stout, and that helps us in protections and in the running game, obviously, too. We just need to get our best guys on the field that are healthy and ready to go."