Holder was driven by a security detail to the MedStar Washington Hospital Center for treatment, officials said. He was described as “alert and conversing with his doctors,” according to Brian Fallon, the attorney general’s chief spokesman.

Fallon added that Holder was “resting comfortably and in good condition” and was expected to “undergo further evaluation.” It was unclear how long he might be hospitalized.

Holder, 63, has served for five years as attorney general under President Obama, after earlier serving as deputy attorney general in the Clinton administration in the late 1990s. The country’s 82nd attorney general, he is an avid basketball player and considered in good health.

Holder also, however, has been under often relentless pressure as attorney general, mostly from GOP lawmakers investigating the Fast and Furious gun-tracking scandal and, more recently, as he has stepped up his activities defending gay-marriage rights and opposing restrictions on voting rights.

Last June, Holder was asked at a Senate committee hearing when he might decide to step down. “The tipping point might be fatigue,” he said then. “You get to a point where you just get tired.”