Singer Natalie Cole has been checked into a NYC hospital since last Friday, a source tells Usmagazine.com.

In July, Cole announced she has hepatitis C.

"She was doing press in New York last week when she got really sick due to chemotherapy she was undergoing to treat her hepatitis," the source explains. "She got anemia from the treatment."

The 58-year-old jazz and R&B singer-songwriter - daughter of Nat King Cole - has won eight Grammy Awards over her career.

Cole wrote about her struggles with drug abuse in her 2000 autobiography Angel on My Shoulder. She admitted to using LSD, heroin and cocaine.

"I've been so fortunate to have learned so much from my past experiences," Cole said in a statement in July about her diagnosis. "I am embraced by the love and support of my family and friends; I am committed to my belief in myself and in my abiding faith to meet this challenge with a heartfelt optimism and determination. This is how I intend to deal with this current challenge in my life."

In February, Cole slammed the Grammy Awards for honoring Amy Winehouse.

"It's a slap in the face to musicians and artists who work very hard that they turn around and give it to someone who really obviously doesn't have a grasp of what she has," she said. "I've been in this business over 25 years and I sacrificed five years of my own life on drugs and almost lost my life because of it."

News of Cole's hospitalization was first reported by ET.