Limbaugh said he was being released from The Queen's Medical Centre, Honolulu, where he was taken on Wednesday after feeling unwell while on holiday in Hawaii.
Doctors said he did not have a heart attack or signs of heart disease.
"The pain was real, and they don't know what caused it," Limbaugh said.
Asked whether he was taking painkillers, Limbaugh said no.
In 2003, he acknowledged an addiction to painkillers for severe back pain and took a five-week leave from his radio show to enter rehab.
More than 14 million people hear Limbaugh at least once a week, making him America's highest-rated broadcaster.