Senator John Fetterman was admitted to hospital on Wednesday after feeling lightheaded during a Democratic retreat, his office said.
Initial tests at the George Washington University Hospital in Washington did not show evidence of a new stroke, the statement released on Wednesday night said.
He remained in hospital overnight for observation and doctors were running more tests.
“He is in good spirits and talking with his staff and family. We will provide more information when we have it,” communications director Joe Calvello said.
Mr Fetterman, a freshman senator, suffered a stroke in May 2022 during his campaign against Republican challenger Mehmet Oz.
His stroke was “caused by a clot from my heart being in an A-fib rhythm for too long”, Mr Fetterman said at the time.
The Democrat returned to the campaign trail a couple months later.
Mr Oz made Mr Fetterman's health a prominent issue throughout the race.
“I had a stroke. He’s never let me forget that,” Mr Fetterman quipped during their October 25 debate.
The effects of the stroke still lingered during Mr Fetterman's debate against his challenger in October, where the Democrat at time struggled to put sentences together.
Mr Fetterman was sworn into office in January.