Pop star Selena Gomez revealed today that she underwent a kidney transplant over the summer. She uploaded a post on her official Instagram account that showed her in a hospital beside her friend, who donated the organ.

The "Good For You" singer said that fans had been wondering why she had been "laying low" over the summer.

"I found out I needed to get a kidney transplant due to my Lupus and was recovering. It was what I needed to do for my overall health," she said.

Gomez, who has 126 million Instagram followers, also revealed that the donor was her longtime friend Francia Raisa, an actress best-known for her role in TV series "The Secret Life of the American Teenager".

At the time of writing, Gomez's post had over 2.4 million likes on Instagram.

Gomez's representatives were not immediately available for comment.