At 12:35 Central European Summer Time (CEST) of the second day of a pre-season test session at the Circuit de Barcelona-Catalunya in February 2015, Alonso lost control of his McLaren MP4-30 at about 215 km/h (134 mph) and crashed into a right-hand side barrier at the exit of the track's third corner.
He did not lose consciousness upon impact only going into that state when he was  administered medication en route to the circuit's medical centre by ambulance.
After doctors checked his condition, he was airlifted by helicopter to the Hospital General de Catalunya (English: General Hospital of Catalonia) in Sant Cugat del Vallès, Barcelona forty minutes later, where he underwent CT and MRA scans which discovered that he had sustained a concussion.
Alonso was released from hospital three days later on 4 March and recuperated at his home in Oviedo.

Before the season-opening Australian Grand Prix, he was subjected to tests to address his reflexes and undertook activities to determine the state of his memory.
Doctors advised Alonso afterwards to miss the Australian race to minimise the risk of second-impact syndrome.
McLaren's test and reserve driver Kevin Magnussen replaced him in Australia.
Alonso meanwhile requested to the McLaren team principal Éric Boullier that he be granted access to their interactive data system and was in daily conservation with Boullier.
He went to the University of Cambridge on 22 March to undergo FIA-assessed memory examinations and reflex tests with three independent physicians to establish how much he had recovered.
Alonso passed the tests.
He was then required to meet Jean-Charles Piette, the FIA's medical delegate, and a chief medical officer in Kuala Lumpur for an impact test, a 40-minute examination to analyse his race craft with comparisons of reaction and cognitive skill scores used from an earlier test.
Alonso was passed fit to compete in the Malaysian Grand Prix.

 
He endured a difficult season as the McLaren-Honda package was unreliable and lacked straight-line speed.
Alonso scored points twice during the year: a tenth-place at the British Grand Prix followed by a fifth at the Hungarian Grand Prix.
He finished 17th in the drivers' championship with 11 points, five behind teammate Jenson Button.
Alonso was dissatisfied with the lacklustre straight-line performance, which became evident after multiple team radio complaints throughout the season.
Alonso said he was frustrated at the team's reliability trouble and urged them to improve on it for 2016.
At 12:35 Central European Summer Time (CEST) of the second day of a pre-season test session at the Circuit de Barcelona-Catalunya in February 2015, Alonso lost control of his McLaren MP4-30 at about 215 km/h (134 mph) and crashed into a right-hand side barrier at the exit of the track's third corner. He did not lose consciousness upon impact only going into that state when he was  administered medication en route to the circuit's medical centre by ambulance. After doctors checked his condition, he was airlifted by helicopter to the Hospital General de Catalunya (English: General Hospital of Catalonia) in Sant Cugat del Vallès, Barcelona forty minutes later, where he underwent CT and MRA scans which discovered that he had sustained a concussion. Alonso was released from hospital three days later on 4 March and recuperated at his home in Oviedo. 
Before the season-opening Australian Grand Prix, he was subjected to tests to address his reflexes and undertook activities to determine the state of his memory. Doctors advised Alonso afterwards to miss the Australian race to minimise the risk of second-impact syndrome. McLaren's test and reserve driver Kevin Magnussen replaced him in Australia. Alonso meanwhile requested to the McLaren team principal Éric Boullier that he be granted access to their interactive data system and was in daily conservation with Boullier. He went to the University of Cambridge on 22 March to undergo FIA-assessed memory examinations and reflex tests with three independent physicians to establish how much he had recovered. Alonso passed the tests. He was then required to meet Jean-Charles Piette, the FIA's medical delegate, and a chief medical officer in Kuala Lumpur for an impact test, a 40-minute examination to analyse his race craft with comparisons of reaction and cognitive skill scores used from an earlier test. Alonso was passed fit to compete in the Malaysian Grand Prix.
 
He endured a difficult season as the McLaren-Honda package was unreliable and lacked straight-line speed. Alonso scored points twice during the year: a tenth-place at the British Grand Prix followed by a fifth at the Hungarian Grand Prix. He finished 17th in the drivers' championship with 11 points, five behind teammate Jenson Button. Alonso was dissatisfied with the lacklustre straight-line performance, which became evident after multiple team radio complaints throughout the season. Alonso said he was frustrated at the team's reliability trouble and urged them to improve on it for 2016.
Motor racing career of Fernando Alonso