The 21-year-old had been due to face Australian Open champion Roger Federer after beating world number two Novak Djokovic but he has had to withdraw.
In a statement released on his Twitter account Kyrgios said he had been sick throughout the night and felt he needed to be at his best in order to face Federer.
He added that, at this stage, he and his team think that it is food poisoning, he also apologised to the fans who had come out to watch the game.
The Australian's statement in full read:
"Unfortunately I am unable to play today due to sickness. At this stage we think it's food poisoning, and I'm praying that it is nothing more.
After a restless night of being sick I have nothing left and to play a great champion like Roger, I need to be at my best to have a chance.
"I don't take this decision lightly, these are the matches we train for but I'm in no fit state to take to the court. I'm sorry to the fans that I'm unable to take to the court but I have to put my health first and I hope you understand.
"I want to wish Roger the best of luck for the rest of the tournament and thank every one for their support so far here at the BNP Paribas Open. I will definitely be back. Thank you."
Kyrgios had drawn a lot of praise for the focus that he had shown during the tournament so far and his withdrawal will come as a big blow for his fans.
Federer will now face the winner of the match between Jack Sock and Kei Nishikori.
The Swiss sent his own message of condolence to Kyrgios after the announcement.
Federer, who defeated great rival Rafael Nadal in the previous round, posted on Twitter: "Hope you feel better @NickKyrgios."
Federer will meet Jack Sock in the last four after the American reached his first Masters 1000 semi-final by beating Kei Nishikori.
The 24-year-old won 6-3 2-6 6-2 to record the first victory over a top five player.
Stan Wawrinka meets Pablo Carreno Busta in the other semi-final.
Read the original article on Eurosport: Federer to face Sock in last four after Kyrgios withdrawal