Fernando Alonso says he does not know whether he will be able to race in this weekend's Chinese Grand Prix.
The McLaren driver was ruled out of the last race in Bahrain because of a broken rib sustained in his terrifying accident in Australia.
The two-time champion said: "Until I get the all-clear from the doctors to race, we cannot assume anything."
The Spaniard, 34, will be examined by doctors of governing body the FIA at the track on Thursday.
Alonso has been unable to do his normal full training programme in the two-week gap between Bahrain and China as a result of his injury.
Last week, he posted images of himself on social media returning to training and wrote: "Happy with how things are going."
Alonso spent the weekend at a luxury resort in Tuscany before flying to the Far East.
If he cannot race in Shanghai, he will again be replaced by McLaren's reserve driver Stoffel Vandoorne.
The 24-year-old Belgian impressed in Bahrain by out-qualifying team-mate Jenson Button on his grand prix debut and scoring a point for 10th place.