Kasey Kahne won't return to the NASCAR Cup Series this season and indicated Tuesday that he might never be able to return to full-bodied stock cars.
Kahne, who announced in August that he would not race in NASCAR regularly starting in 2019, has missed the last five races as he has worked with doctors to determine why he is suffering severe dehydration during races.
A test last week at Charlotte Motor Speedway didn't show enough progress. Six races remain in the 2018 season.
"To say I'm disappointed after receiving the result that I was not medically cleared for the remainder of the season following a test session at Charlotte Motor Speedway last week is an understatement," Kahne posted in a statement on social media.
"It was my hope that everything would go well and I would be able to finish out the season strong in the #95 for Leavine Family Racing. Unfortunately, that's not the case."
During the final 100 laps of the Sept. 2 race at Darlington Raceway, Kahne had difficulty seeing and was feeling nauseous because of dehydration. He was sweating so profusely, he could not keep enough water in his body and then felt too sick to drink more water. He had suffered similar, but not as severe, symptoms in at least three races prior to Darlington over the previous 14 months.
"Out of the race car I am perfectly healthy, I feel great, and the doctors have determined that I have no underlying health problems," Kahne wrote.
"My body just can't handle extended periods of time in the race car and we weren't able to control the sweat ratio to keep me hydrated enough to prevent any permanent damage to my body."
The 38-year-old Kahne has 18 Cup wins and 93 top-5s in 529 career starts.
Kahne, whose roots are in sprint-car racing and owns sprint-car teams, plans to continue to race in those events.
"NASCAR has been a great home for me for 15 years and I wish the #95 the best of luck these last few races," Kahne wrote. "I am looking forward to getting back in a sprint car soon. With much shorter races and open cockpits, there is no issue with my health or hydration with that type of racing.
"See you all soon at the dirt tracks, and thank you for sticking with me over the years."