"Sen. Glenn is at The James Cancer Hospital at The Ohio State University (and) was admitted there more than a week ago," Wilson wrote in an email. "I do not know his condition or illness or prognosis. I caution that even though Sen. Glenn is at The James that does not necessarily mean he has cancer."
He became the first American to orbit the Earth in 1962.
Glenn piloted the Mercury space capsule, dubbed Friendship 7, and circled the planet three times in just under five hours on February 20, 1962. Of the original seven US astronauts who made up Project Mercury -- Glenn, Alan Shepard, Gus Grissom, Gordon Cooper, Scott Carpenter, Walter Schirra and Donald Slayton -- Glenn is the last surviving member.
Prior to his career as an astronaut, Glenn flew 149 missions during World War II and the Korean War and received multiple medals and decorations, including the Distinguished Flying Cross on six occasions.
He resigned from the astronaut program in 1964 and pursued a career in politics, serving as a US senator as a Democrat from Ohio between 1974 and 1999. He even ran for president in 1984. But Glenn's time in space wasn't over.
At 77, he became the oldest person to ever travel in space. Glenn was a payload specialist aboard the space shuttle Discovery for a nine-day mission in 1998.
In 2011, he received a Congressional Gold Medal alongside Neil Armstrong, Buzz Aldrin and Michael Collins. In 2012
, he received the Presidential Medal of Freedom from President Obama.
This year, he attended a celebration that saw the renaming of Port Columbus Airport to John Glenn Columbus International Airport.
Glenn and his wife, Annie, have been married for 73 years. Together, they have two children.