In an Instagram post, the singer says that her friend Francia Raisa donated an organ to her and says she wanted to explain why fans hadn't heard much from her despite having new music out.
"So I found out I needed to get a kidney transplant due to my Lupus and was recovering," she writes.
"It was what I needed to do for my overall health."
Selena Gomez also thanked her friend, The Secret Life of the American Teenager actress Francia Raisa, in her Instagram post.
"There aren't words to describe how I can possibly thank my beautiful friend Francia Raisa," she writes.
"She gave me the ultimate gift and sacrifice by donating her kidney to me. I am incredibly blessed. I love you so much sis."