Span played Monday night, starting in center field and going 0-for-4, but said he didn't feel right during the game and told team doctors about his problems after the Twins' 6-4 win.
"As the game went on, I didn't feel like myself," Span said. "I didn't have the energy I would have and I felt spaced out. I just knew I wasn't myself. So that's where we are."
Span, who collided with Royals catcher Brayan Pena on Friday, said the dizziness feels much like the symptoms he experienced in 2009 when he missed two weeks with vestibular neuritis.
He was tested for a possible concussion in Kansas City and it was ruled out, but Twins trainer Dave Pruemer said Span will still undergo precautionary tests on Wednesday.
"We want all our bases covered," Pruemer said.
Span also admitted that the symptoms dating back to his bout with vestibular neuritis two years ago have never fully gone away and he underwent an MRI on his brain over the offseason. The results came back negative, which Span called a relief, but he said he's worried that his symptoms have returned.
"I'm definitely scared," Span said. "I want to get this checked out. I'm definitely frustrated and all those things. I'm not able to go out there and perform to my capabilities, and that's frustrating, because this team is starting to turn things around. So I want to get back and get it checked out."
If Span does have a concussion, he could be placed on Major League Baseball's new seven-day disabled list. Ben Revere will play center field in Span's absence.
"You can't use the seven-day DL until somebody decides what he has," Twins manager Ron Gardenhire said. "That's why we're getting him checked out."