"Dog the Bounty Hunter" Duane Chapman is suffering from a pulmonary embolism in the heart.
"You're a ticking time bomb," Dr. Mehmet Oz told Chapman in a preview of Monday's episode of "The Dr. Oz Show."
"You're not going to be here with the heart the way it is right now. Fear of death is normal. I'm surprised you don't fear death when you're chasing after convicts. But when you run away from doctor, that means you have to do your own doctoring."
The 66-year-old reality TV star was hospitalized two weeks ago for chest pains.
He is now taking blood thinners, eating a healthier diet and trying to quit smoking.
His wife, Beth Chapman, died of cancer in June. She was 51.
"I don't want to die right now. I'm not afraid to die anymore, but I really didn't care for awhile if something would happen. I do care now," Chapman told People magazine after the clip for "The Dr. Oz Show" was released on Friday.
Chapman can now be seen on the WGN America series, "Dog's Most Wanted."
WGN America