"Suzanne Thabet has been moved to the intensive care unit at Sharm el-Sheikh hospital after suffering a heart attack," state TV said, referring to Egypt's Red Sea resort.
Mohammed Fathallah, who heads the hospital, said Mrs Mubarak had suffered a "suspected heart attack and a sharp increase in blood pressure."
"She will be kept under observation," he said in a statement.
The news came hours after the Illicit Gains Authority ordered Suzanne Mubarak's detention for 15 days on charges of illegal acquisition of wealth and as preparations were underway to move her to prison.
Former president Mubarak, who was detained on April 13, is in custody at the same hospital in Sharm el-Sheikh after having reportedly suffered a heart attack when he was first questioned.