The donor is another actress.
Selena Gomez has been spotted on a movie set just hours after revealing she underwent a kidney transplant due to her battle with Lupus.
Read: James Corden Takes 'Carpool Karaoke' to the Next Level With Selena Gomez and a Roller Coaster
Gomez, 25, took to Instagram Thursday morning to announce that her friend, actress Francia Raisa, donated her kidney to the singer to save her life.
"She gave me the ultimate gift and sacrifice by donating her kidney to me," the Spring Breakers star revealed.
The news solves the mystery of why Gomez has kept such a low profile this summer.
She released new music but didn't make public appearances to promote it and it turned out she was recovering from surgery that left her with a long scar across her stomach.
Gomez, a Texas native, was recently seen at the Hand in Hand telethon for Hurricane Harvey and Irma victims Tuesday night where she made an impassioned plea for donations and help for Houston.
Read: Selena Gomez Returns to Stage After Rehab: 'If You Are Broken, You Do Not Have to Stay Broken'
Dr. Travis Stork from The Doctors explained to Inside Edition how Lupus could require a kidney transplant.
"This is going to be a long road for her," he said. "There is a positive. She is 25, and she is still youthful."
More than 1 million suffer from lupus, which is a serious auto-immune disease, and like Gomez, 33-year-old Alison Lee suffers from lupus and had a kidney transplant last year.
She told Gomez to "stay positive," "be careful of germs" and wash her hands all the time.
Her donor was her mother.
There are more than 93,000 people currently on the waiting list for an anonymous kidney donor, some on it for as long as 10 years.
The process can, however, be sped up if the donor is a family member or friend, as was the case with Gomez.
Watch: 4-Year-Old Celebrates Anniversary of Heart Transplant With Stitched-Heart Cake
