An ambulance was called to the family vacation home on the Massachusetts island around 3:30 p.m., when Heinz Kerry began to have symptoms "consistent with some sort of seizure," a source close to the family said.
Heinz Kerry's husband, Secretary of State John Kerry, accompanied her to Nantucket Cottage Hospital and then to Massachusetts General Hospital in Boston, where she was transferred once her condition stabilized Sunday night.
She was being held at MGH for evaluation Monday.
“The family is grateful for the outpouring of support it has received and aware of the interest in her condition, but they ask for privacy at this time,” said Glen Johnson, a spokesman for Kerry.
Heinz Kerry, 74, is a survivor of breast cancer. She was diagnosed in 2009 and later deemed cancer-free.
Notable deaths of 2014 [PHOTOS]
Soviets call Reagan joke 'dangerous' [ARCHIVE]