Dole, 89, has left Walter Reed and is "doing fine," the aide told NBC News.
Majority Leader Harry Reid said on the Senate floor Tuesday Dole called him a few days ago to let him know he was at the hospital, ABC News reported.
Dole was the Republican presidential nominee in 1996 and was President Gerald Ford's running mate in 1976. He represented Kansas in the U.S. Senate from 1969 to 1996 and served in the U.S. House of Representatives from 1961 to 1969.
He was Senate majority leader from January 1995 until June 1996.
Dole was hospitalized in January 2011 for treatment of a minor infection, two months after he had been discharged following a 10-month stay at Walter Reed while he recovered from pneumonia following knee surgery. He was hospitalized in 2009 for multiple problems related to a skin graft procedure.
He was hospitalized at Walter Reed for 40 days after doctors determined he had internal cranial bleeding following hip replacement surgery in December 2004.