Felipe Massa was taken to hospital following the conclusion of free practice at the Hungaroring on Friday for precautionary checks after feeling unwell with a suspected virus.
The Brazilian was taken for checks after feeling dizzy when he got out of the car, and after cancelling his post-session media duties to visit the medical centre to see doctors.
He was transferred to the MH EK Honvedkorhaz hospital in Budapest for further tests, but after further examinations, no serious problem was found and Massa was released, and was spotted at the Hungaroring track on Saturday morning.
He will participate in final practice but after the session he will be examined again, and should he be deemed not fit enough to race, Paul di Resta is in line to step in to replace him alongside Lance Stroll.
Di Resta is the Williams Martini Racing reserve driver in 2017, but last competed in Formula 1 back in the 2013 Brazilian Grand Prix for the Sahara Force India F1 Team, whilst in recent years he has been competing in the DTM Series with Mercedes.
It had been a difficult day of practice for Massa on Friday, with two spins in quick succession in the afternoon session, whilst his best time was only good enough for fifteenth fastest, just behind team-mate Stroll.