Brian Vickers will miss the remainder of the season, he said at a news conference on Friday.
During a 38-minute interview session in which the Red Bull Racing driver offered specific details of his condition, along with his doctor and a Red Bull team official, Vickers said blood clots in both of his lungs and left leg will require blood-thinning medications that do not permit him to race.
Vickers, 26, said he plans to return next season for the Daytona 500. Red Bull general manager Jay Frye said Casey Mears will continue to drive the No. 83 in the foreseeable future, except perhaps at road courses.
"I will be out of the car for a minimum of six months; the rest of the year," Vickers said in a room packed full of reporters. "As you can imagine, that is killing me – no pun intended. I really miss being back in the car."
Vickers' doctor, Steven Limentani, said it was not advisable for anyone to race while on blood-thinning medications, which increase the risk of external and internal bleeding.
As Vickers put it: "I can race and be on blood thinners, I just can't crash."
Vickers was visiting Washington, D.C. two weeks ago when he woke up with chest pains and had trouble breathing. He rated the pain a '10' on a scale of 1-10, but said he brushed it off and went back to sleep.
The next day, however, the pain persisted, and he called a doctor who recommended he go to the emergency room.
Doctors found the blood clots on a CT scan and admitted Vickers to a Washington-area hospital. He was released two days later, but had more pain upon his return to Charlotte and was readmitted on the day of last week's Dover race.
No one is quite sure what caused the clots, and Vickers' doctor said the clots were not common for a healthy 26-year-old male.
"We're not going to speculate," Vickers said. "We've had some tests come back, we have not had all of the tests come back."
Vickers said he'll fill his absence from the car by taking some time off and resting, but also attending races and getting another view of how the sport operates.
"It sucks," Vickers said. "This is my life and what I love to do. And I fully intending on doing it again."
But Vickers, displaying a positive attitude and sense of humor, made it clear that he was grateful to be alive.
"I'm very fortunate," he said. "Thank God I'm still alive."
Vickers won the first race for Red Bull Racing last summer at Michigan and made the Chase for the first time. This season was more of a struggle, as he had just three top-10 finishes in 11 starts.
Mears was 22nd in his debut for the team last week at Dover.