The 73-year-old entertainer's physician Dr. Elaine James told the Riverside Press-Enterprise that the singer's chronic leukemia was declared incurable two weeks ago.
The doctor has been caring for James, who is best known for her 1961 hit 'At Last,' since March 2010 at the singer's Riverside home, where she is now under 24-hour medical care and has been placed on oxygen.
"She's in the final stages of leukemia. She has also been diagnosed with dementia and Hepatitis C," the New York Daily News quoted the singer's longtime manager Lupe De Leon as saying.
"Her husband is with her 24 hours a day, and her sons visit regularly. We're all very sad. We're just waiting," De Leon said
The doctor said that she is spreading word of the singer's condition so others will pray for her.
She said that fans knew James had been sick "but not how sick."
Court records in the singer's probate case also show she suffers kidney failure.