Glenn Frey was left sick and suffering during his dying days because of the poor treatment at a hospital ... according to a new suit filed by his widow.
Cindy Frey alleges the Mount Sinai Hospital in New York and Steven Itzkowitz failed to properly render medical care to her husband -- the co-founder and guitarist for the Eagles -- the last couple months of his life ... until he died in January 2016.
Cindy claims the medical workers were negligent in treating Frey's ulcerative colitis, failed to properly assess respiratory issues, failed to treat infection, failed to consider side effects of medications and didn't properly advise him of the risks to his health and life.
According to the docs, first reported by the NY Post ... Frey was "rendered sick, sore, lame and disabled, suffered injuries, pain, mental anguish ... and was permanently injured and disabled until the time of his death."
Cindy's asking for damages for wrongful death.