The doctors ran "multiple tests", however, found that there was "no scientific explanation" for her breathing issues.
She explained, "They ran multiple tests, multiple times, and there's nothing physically wrong with me. So, wonder why I was there."
In true Sarah style, the brunette beauty was in good spirits on Friday while in her hospital gown and hooked up to a machine, dancing for the camera to wish her friend a happy birthday.
WATCH: Sarah Hyland dances in the hospital despite her illness
And what else does one do when bored in the hospital? Take a glam selfie!
For Sarah, she is no stranger to hospital visits with her ongoing health issues. The star suffers from kidney dysplasia, a condition that means her kidneys did not develop properly when she was still in the womb. Now, she suffers from painful cysts, which led to a second kidney transplant in recent years.
She also suffers from endometriosis, a painful disorder where the tissue that is meant to line the inside of her uterus, has grown on the outside.
She has also had multiple surgeries for this condition.
As expected, her health battles have gotten her very down in the past. Thankfully, she stars mental health has improved since dating boyfriend Wells Adams last year.
At the time of her surgery, she said, "He was texting me in the morning before I went into surgery, and we were FaceTiming the entire time I was in the hospital.
"He's seen me at my worst. He was there through all of that. I think that's why I feel the most beautiful in his eyes, because he still finds me beautiful after seeing all that."
Hopefully, Sarah feels better ASAP!