The 21-year-old singer, who was reportedly diagnosed with the disease a few years ago, cancelled her tour to regain her health, reported Huffington Post online.
Lupus is believed to be a kind of diseases, in which the human immune system becomes hyperactive and attacks normal, healthy tissues.
"Selena has been going full throttle the past few years and her Lupus is really catching up with her right now," a source said.
"Selena knows that she needs to take some time to address the disease and look after herself better if she wants to live a full and healthy life," the source added.