Spokesman Jim McGrath said the 93-year-old was admitted to Houston Methodist Hospital on Sunday morning. Doctors were treating him for an infection that spread to his blood.
"He is responding to treatments and appears to be recovering," McGrath said. "We will issue additional updates as events warrant."
Bush's hospitalization came less than a day after the funeral of former first lady Barbara Bush, who died Tuesday at age 92. More than 1,500 friends and family members attended the private service at St. Martin's Episcopal Church in Houston to pay their respects.
Barbara Bush had congestive heart failure and chronic obstructive pulmonary disease in the years before her death.
Bush, the oldest-living former president -- and longest-lived president in U.S. history -- has vascular parkinsonism, a form of Parkinson's disease.