In her weekly blog for People, the restaurateur/reality TV star, 53, writes about the shock of fainting and how her jet-setting life got the best of her.
"I had to take off to New York for work Tuesday right after the elimination show. That night I took a red eye flight at 11 p.m., arriving in New York at 6 a.m. and heading straight to six hours of rehearsals upon landing.
After rehearsals, I ran back to my hotel for a quick change and headed to the Bravo Upfronts party, which wasn't over until around 11 p.m. Then I had a light dinner and drink, and went to bed.
After a few hours of sleep, I was up bright and early at 6 a.m. to prepare to dance with my partner Gleb on Live with Kelly and Michael. We were performing an encore of the Viennese waltz, which I ended up doing barefoot! Then off we went to six hours of rehearsals again before catching a flight back to L.A. that evening.
By the time Thursday rehearsals rolled around – let's just say I was exhausted and everything felt off. Gleb and I were rehearsing our cha cha and suddenly I just blacked out.
I was in shock when I woke up. I fainted only once before in my life. The doctor found that I had a viral infection with fever and swollen glands. And between trying to fight that and all of the stress on my body from running around, I ended up with low blood pressure and a rapid heart rate, which is why I fainted."
Lisa also writes that she still feels a bit under the weather, but she promises to give it her best when she dances the cha Cha Monday night with Gleb.
Dancing with the Stars airs Mondays at 8/7c and Tuesdays at 9/8c on ABC.