Mrs Bush, after consulting relatives and doctors, had decided to focus on comfort care at the family home in Houston.
"She is surrounded by a family she adores, and appreciates the many kind messages and especially the prayers she is receiving," said the office of former president George H W Bush.
Mrs Bush was treated for bronchitis in 2017, had heart surgery in 2009, and was operated on for an ulcer in 2008. She has been treated for the thyroid ailment Graves' disease.
AGENCE FRANCE PRESSE