A spokesman for Dick Cheney said the former U.S. vice president was admitted to a hospital Friday after feeling unwell.
Cheney, who has a long history of heart problems, was admitted to the George Washington University's hospital for tests. His office said he is expected to remain in the hospital for a few days.
Cheney has had five heart attacks, the first in 1978 when he was 37 years old. He suffered his last heart attack in February.
In 2001, Cheney had a heart defibrillator implanted to monitor his heart and shock it back into a normal rhythm if abnormal beating occurred.
Some information for this report provided by AP, Reuters and AFP.