Alonso went off between turns 3 and 4 at the Circuit de Catalunya, with the right-hand side of the car hitting the wall on the inside of the track. The car was not heavily damaged in the incident, but Alonso was transported to the circuit's medical centre before being transferred to hospital.
McLaren issued a statement explaining that Alonso is conscious and talking, describing the checks as "precautionary" following the incident.
"Fernando was driven to the circuit's Medical Centre where the circuit's doctors gave him first aid," a McLaren statement read.
"He was conscious and spoke with the doctors.
"However, as per usual procedure in such circumstances, he was then airlifted to hospital where he is undergoing precautionary checks."
Jenson Button was scheduled to drive the MP4-30 in the afternoon session, but the team has yet to confirm if the car will run again on Sunday.
Click here for the gallery from day four of the second test