In his return to The Tonight Show on Monday, the funnyman didn't give any details of his illness (his rep said earlier it was apparent dehydration), but he came back with plenty of jokes about it.
"What happened was – and I think this was a mistake – I ate a raw pig a friend brought back from Mexico," Leno, 58, said in his monologue.
He also found out he had a "really bad HMO," saying, "For X-rays, they had to take me over to Burbank Airport and put me through the baggage."
And he was able to tie his illness to the other big Leno news: the changeover of The Tonight Show hosting chair to Conan O'Brien.
"Have you ever slept in a hospital? I spent the night. I was there for 24 hours," he said. "I had a horrible dream that I couldn't breathe. I felt like I was suffocating. Then I woke up and realized Conan was holding a pillow over my face."
Reporting by PAMELA WARRICK