Alyson Hannigan had much more to overcome than nerves before Tuesday’s episode of Dancing with the Stars.

The How I Met Your Mother actress, 43, revealed that she had been feeling “very ill” with a migraine ahead of the show’s taping and didn’t know whether she would even be able to dance.

“I was very, very ill this morning,” Hannigan told. “I had a migraine that really took me down and, yeah, I couldn’t even keep fluids down. I didn’t think I would make it through today.”

Though she said she was “feeling much better” at the end of the night, her dance partner Sasha Farber said he was very concerned when he got on the phone with her earlier in the day.

“As soon as I saw Alyson on my phone at [6:45 a.m.], I was like, Something’s not right,” Farber said. “And just her voice … as soon as I heard her voice, I was like, Oh, that’s it. And she was crying.”

“She couldn’t get out of bed. She couldn’t get to work,” he continued. “So actually, fun fact: usually when we get to work, we run it twice and then we do a dress run. She didn’t run that because she couldn’t walk — so she missed all that rehearsal.”

Meanwhile, Hannigan said she had been struggling to overcome the illness in her trailer hours before the show.

“I was in my trailer in the fetal position,” she explained. “It was awful. I was just like, I couldn’t take 10 steps without having to throw up.”

While Hannigan noted that her official diagnosis was a “really bad migraine,” she said she’s learned a lot more about how such a simple thing can affect her health.

“Apparently migraines, you can also be throwing up. But I didn’t know that,” she explained. “And I was just like, ‘But I didn’t have a fever. I didn’t have COVID,’ all this stuff. But, yeah, apparently migraines can get that serious. And now I know.”

As for how she eventually got well enough to take center stage on the ballroom Monday night, her partner, 39, attributed it to “medicine” as well as her strong will to overcome the illness to put on a solid performance (which earned her a judges’ score of 24).

“This one is such a hard worker and she has so much, she has so much soul and power, and she worked so hard,” he shared. “That’s why she floated tonight on a glitter canoe.”

Dancing with the Stars airs Tuesdays at 8 p.m. ET/5 p.m. PT on ABC and Disney+.