The actor first suffered ill health in Aspen in January, when he was hospitalised for "mild kidney failure". He sought emergency medical treatment again in February for blood clots in his lungs and an enlarged ventricle in his heart.
Cannon has now revealed that his doctors have diagnosed him with autoimmune disease which he will have to live with for the rest of his life.
"It's a lot of stuff, but it's all in order now," the America's Got Talent judge told People. "They kind of say [my] autoimmune [disease] is like a lupus-type of thing, but no-one else in my family has it."
Cannon further explained that he was very lucky to have been diagnosed with the illness before it took his life.
"I feel blessed to be alive. If it wasn't discovered, I don't know [if I would have lived]," he commented.
Cannon has lessened his work commitments on the advice of his doctors, including quitting his New York City radio show.
The entertainer also discussed his personal life this week and revealed that his and Mariah Carey's twins Monroe and Moroccan are very verbal and "love to sing".
> Mariah Carey brings forward comeback performance
> Nick Cannon to direct first movie: 'It will be a modern House Party'