Sergio Perez was rehydrated with the help of an IV drip after qualifying in Malaysia.
The Mexican told the media he has been suffering from a stomach virus.
"This is possibly the worst place to not feel 100 per cent," said the Force India driver.
As they spoke with the 27-year-old, reporters noticed that Perez had a ’band-aid’ plaster on the inside of his forearm.
He confirmed: "I had to replace all the fluid that I have lost in this way.
"I suffered a lot in qualifying and this is the hardest race on the whole calendar, so it will be difficult for me."