Selena Gomez was absent from headlines most of the summer and this morning she took to Instagram to reveal why.

The 25-year-old singer had a kidney transplant.

In the post she thanked her friend and donor, Francia Raisa, who is known for her role in The Secret Life of an American Teenager, saying,

“There aren't words to describe how I can possibly thank my friend Francia Raisa. She gave me the ultimate gift and sacrifice by donating her kidney to me. I am incredibly blessed.""

Gomez has had to lay low before. She was diagnosed with Lupus in 2013 and did a round of chemotherapy to combat the autoimmune disease. Last year she took time off to combat the anxiety and depression that comes with having a life-altering disease.

Kidney problems in people diagnosed with Lupus are fairly common - not from the disease itself, but from the medications used to treat the symptoms, according to Lupus.org. There are other complications from Lupus that can damage the kidneys as well as other major organs in the body, such as the heart and lungs.

According to Kidney.org, Lupus does not usually recur in the transplanted kidney. However, the kidney itself is only a temporary fix as they last at the very most 15 years. Living donor organs last longer than deceased donors, particularly in kidneys. Find out how to become a living donor at UNOS.com.