"What happened was – and I think this was a mistake – I ate a raw pig a friend brought back from Mexico," Leno, 58, joked in his opening monologue.
He also found out he had a "really bad HMO," added that, "For X-rays, they had to take me over to Burbank Airport and put me through the baggage."
"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."
While his rep has yet to release any details of his sickness, he was reportedly hospitalized due to "dehydration," which some reports claim was the result of food poisoning.
We're just glad to hear that he made a speedy recovery! Check out the hilarious video from Monday nights taping below...