The 50-year-old rocker reportedly had trouble breathing during sound check.
Smash Mouth's leading man was reportedly struggling with a health issue that led him to canceling one of the band's shows.
According to TMZ, Steve Harwell went to the hospital on Thursday after complaining of having breathing problems during a sound check, and told the tour manager that he would be unable to take the stage that night.
Harwell spoke to the website, and said that doctors informed him that he was suffering the effects of his cardiomyopathy, which is a condition that makes it hard for the heart to deliver blood to the body, and can lead to heart failure.
According to the 50-year-old musician, he has been on oxygen and IVs since being admitted to the hospital and doctors have also prescribed him steroids and inhalers. Harwell also claimed that he has been feeling unwell for the past four days, but it only got really bad on Thursday, leading him to cancel Smash Mouth's show.
Harwell told TMZ that he still plans to perform tonight at the Wildey Theatre in Edwardsville, Illinois.
ET has reached out to Smash Mouth and Harwell's reps for more on this story.