Roger Bergendorff, 57, had been hospitalized since Feb. 14.
He is charged with possession of a biological toxin and two weapons offenses stemming from materials authorities said were found Feb. 26 and Feb. 28 in his room at an extended-stay motel several blocks off the Las Vegas Strip.
"He was released from the hospital and he's in custody," said Agent Joseph Dickey, spokesman for the FBI office in Las Vegas.
The three charges carry a possible penalty of 30 years in federal prison and a $750,000 fine. Bergendorff was scheduled appear Wednesday afternoon before a federal judge in U.S. District Court in Las Vegas.
A six-page complaint alleges that Bergendorff obtained castor beans, from which ricin is derived, by mail in June 2002, and made ricin from them while living in the basement of his cousin's house in Riverton, Utah.
Bergendorff's cousin, Thomas Tholen, 54, was indicted earlier this month in Salt Lake City for allegedly failing to report that the substance was being illegally produced.
Tholen was charged with misprision of felony, which officials said means he had knowledge of a crime but failed to report it.
The manufacture or possession of ricin, a biological agent, is prohibited by federal law. The only legal use for the substance is cancer research.