Doctors at Massachusetts General Hospital in Bostonupdated Teresa Heinz Kerry's condition from "critical" to "fair" this morning, a family spokesman said.
"She is undergoing further evaluation, and Secretary of State John Kerry, her son and other family members remain with Mrs. Heinz Kerry at the hospital in Boston, as they have been since she became ill," said Glenn Johnson, the personal spokesman for Secretary of State John Kerry.
Heinz Kerry experienced "seizure-like" symptoms when, accompanied by her husband, she was transferred from her home in Nantucket, Mass., to the hospital by ambulance Sunday, according to sources. "Once doctors had stabilized her condition, she was transferred to Massachusetts General Hospital in Boston, again accompanied by the secretary," said Johnson.
Doctors have not said what her diagnosis is.
Nantucket Cottage Hospital spokesman Noah Brown, said Heinz Kerry, 74, was admitted on Sunday but would not say why.
Sources close to the family confirmed to ABC News that she was taken from her home to the hospital by ambulance after falling ill, but they did not provide any details of her illness.
The State Department has not released a public schedule for Kerry for this upcoming week. Kerry was slated to meet with Middle East leaders and participate in a strategic dialogue conference with Chinese leaders.
Heinz Kerry, the widow of former Sen. John Heinz, was diagnosed with breast cancer in September 2009. She underwent surgery and radiation treatments, and overcame the disease.
ABC News' Martha Raddatz and Lara Salahi contributed to this report.