James' live-in doctor told the Riverside Press-Enterprise that the singer's chronic leukemia was declared incurable two weeks ago.
Dr. Elaine James, who isn't related to the 73-year-old singer, has cared for her at the singer's Riverside, Calif., area home since March 2010.
Elaine James said she's spreading word of the singer's ailments so people will pray for her. She says fans know Etta James has been sick "but not how sick."
According to records, the singer also suffers from dementia and kidney failure.
Elaine James made her comments outside a Riverside conservatorship hearing over the singer's $1 million estate. The singer's son, Donto James, wants a conservator rather than the singer's husband, Artis Mills.
The Associated Press contributed to this report.