On Monday, the 28-year-old actress posted videos to her Instagram Story, sharing that she had just gotten home from a days-long hospital stay.
"Thank you, guys, who have been sending well wishes while I was in the hospital. Long story short, I went in because I was feeling like I was being choked from whatever is in the house," she said. "And then I was like, 'Maybe it's just a coincidence. Maybe, like, there's actually something medically wrong with me."
"So I go to the ER after a very long day of work with lots of makeup on and I just got home from Friday night," she continued. "They ran multiple tests, multiple times. There's nothing physically wrong with me. So wonder why I was there."
In captions for the videos, Hyland revealed that she "couldn't breathe" and "had chest pains" during her mystery illness for which she said there's "no scientific explanation."
Hyland, who has been diagnosed with kidney dysplasia, has long since dealt with health issues, most recently with a hospitalization back in March after a 104-degree fever.
Back in December, the Modern Family actress revealed that she underwent a second kidney transplant after her body rejected the first donor kidney. ET caught up with Hyland in January, and she said she was "doing really, really well" following her surgery and gushed over spending time with her boyfriend, Wells Adams.
"I just came back from Mexico and that was really, really nice. The good thing about being stable, health-wise, and having an amazing significant other is that now I’m able to travel more," Hyland said at the time. "The last time I took a vacation before this year I was 24. I just turned 28, so I’ve just been either working on my health or working nonstop, so it's really good to be able to do something like that now."
Likewise, Adams only had kind things to say about his girlfriend, who underwent the second transplant shortly after they started dating.
"It's not hard to love her. She's gorgeous and beautiful and smart and talented... With her health issues and stuff, everyone goes through things in their lives, it just so happened that when we started dating she was going through a very big thing," he told ET in February. "But as our lives unfold together, there's going to be things that happen to me when I'm going to lean on her. Every relationship's a give and take."