The 61-year-old Atkins underwent brain surgery last month.
Forty years ago, Atkins confessed to killing pregnant actress Sharon Tate, and earlier this month, Atkins lost her final bid for parole at Chowchilla State Prison. Atkins asked for parole 13 times during her 37 years in incarceration and was turned down every time.
Her attorneys had argued she deserved to be released on compassionate grounds.
Atkins was California's longest-serving female inmate, a distinction that now falls to Patricia Krenwinkle, who was convicted along with Atkins for the Tate-LaBianca murders.
City News Service contributed to this story.