A statement released by the parliament press center said that Khasbulatov, 50, had fallen ill from "extreme fatigue" and "high blood pressure".
Khasbulatov, who was at first accused by lawmakers of being drunk, was examined in his office by his doctor.
His illness occurred at the end of a day of heated debate, over which he presided, on the convening of the parliament's full legislature, the Congress of People's Deputies.
In a public outburst earlier in the day, Khasbulatov told a media seminar that he believed he was being followed and that his phone was tapped.
"I can't say anything in my office without later hearing it somewhere else", he said.
Appearing tired and tense, he made his remarks in the context of sharp criticism of the government, of which he is an outspoken opponent.
"Parliament is the basis of democracy", he told the journalists. "You say hurrah to Gaidar, but in a year everything will fall apart and lead to totalitarianism".
A Message from The Moscow Times:
Dear readers,
We are facing unprecedented challenges. Russia's Prosecutor General's Office has designated The Moscow Times as an "undesirable" organization, criminalizing our work and putting our staff at risk of prosecution. This follows our earlier unjust labeling as a "foreign agent."
These actions are direct attempts to silence independent journalism in Russia. The authorities claim our work "discredits the decisions of the Russian leadership." We see things differently: we strive to provide accurate, unbiased reporting on Russia.
We, the journalists of The Moscow Times, refuse to be silenced. But to continue our work, we need your help.
Your support, no matter how small, makes a world of difference. If you can, please support us monthly starting from just $2. It's quick to set up, and every contribution makes a significant impact.
By supporting The Moscow Times, you're defending open, independent journalism in the face of repression. Thank you for standing with us.
Remind me later.