Newgarden crashed heavily while leading the latter race of the Iowa double-header and would later lose consciousness as he exited a transporter, falling and hitting his head.
He was airlifted to hospital, where all scans came back negative, and released the following morning, but doubts remained about whether he would contest the 13th race of the season.
As it stands, he is only cleared to drive in the sole practice session on the Brickyard road course on Friday morning (local time; late Friday night AEST), after which he will be re-evaluated ahead of Qualifying later in the day.
“Following the event at Iowa Speedway and per IndyCar protocol, the driver of the No. 2 PPG Team Penske Chevrolet, Josef Newgarden, was evaluated this afternoon by IndyCar Medical Director Dr Geoffrey Billows,” read an IndyCar statement.
“Newgarden will be re-evaluated after the session to determine if he's cleared to resume all racing activities for the remainder of the Gallagher Grand Prix event.”
Newgarden's Thursday (local time) evaluation was already set to happen given the size of the hit when his car had an apparent mechanical failure while he looked on to sweep the Iowa event.
However, the fact he collapsed after being released from the medical centre raised questions about IndyCar's medical procedures.
Practice at Indianapolis starts tonight at 23:30 AEST and Qualifying tomorrow morning at 03:00 AEST.
Both those sessions and the race itself will be live and ad-free on Stan Sport.