Barnstable police Sgt. Ben Baxter says a 911 call from the Kennedy compound in Hyannis Port came about 5 p.m. Friday.
Baxter says Kennedy was taken by ambulance to Cape Cod Hospital. He says Kennedy was "alert and responsive" during the trip.
Representatives of Kennedy and the hospital did not immediately return calls seeking comment.
Kennedy had a seizure in May and underwent surgery in June for a malignant brain tumor. After undergoing six weeks of chemotherapy and radiation treatment, he has been increasing his public activity.