Fetterman was taken to George Washington University Hospital after feeling lightheaded toward the end of the Senate Democratic retreat Wednesday, according to a statement from his spokesperson, Joe Calvello.
"Initial tests did not show evidence of a new stroke, but doctors are running more tests and John is remaining overnight for observation," Calvello said.
Fetterman, who was seen smiling and shaking hands at the State of the Union on Tuesday night, "is in good spirits and talking with his staff and family," Calvello said. "We will provide more information when we have it."
The Pennsylvania Democrat uses assistive technology to provide closed captioning in the Senate while he continues to recover from a stroke he had in May.
Fetterman still has auditory processing symptoms, but doctors said in the fall he had no cognitive impairments and could work "full duty" in public office.
Candy Woodall is a Congress reporter for USA TODAY. She can be reached at firstname.lastname@example.org or on Twitter at @candynotcandace.
This article originally appeared on USA TODAY: Sen. John Fetterman, who suffered stroke during campaign, hospitalized