José R. Peralta, the first Dominican-American elected to the New York State Senate, died on Wednesday night in a hospital in Queens, where he represented a diverse constituency. He was 47.

He was taken to Elmhurst Hospital Center after becoming disoriented following a two-week illness, but the cause of death had not yet been determined, a staff member said. An autopsy was scheduled.

Mr. Peralta, a Democrat, lost his re-election bid in September after serving eight years in the State Senate representing neighborhoods in Jackson Heights, Corona, Elmhurst, East Elmhurst and portions of Woodside and Astoria.

A member of a Democratic group that caucused with Republicans, Mr. Peralta was defeated by Jessica Ramos, an insurgent from his own party riding a progressive wave. He was set to leave office at the end of December.

José Rafael Peralta was born on Nov. 10, 1971, in New York City to parents who had emigrated from the Dominican Republic. He attended public schools in Queens and graduated from Queens College, where he studied psychology and sociology and served as student body president.

Though he had been ill for at least two weeks, he had been reluctant to visit a doctor, according to Chris Sosa, his director of communications. After much prodding, he finally went for an exam recently, and he had a follow-up scheduled for December.

“It was like pulling teeth to get him to talk about not feeling well,” Mr. Sosa said. “He just thought he was having symptoms related to getting the flu shot.”

Mr. Peralta was at home with his family on Wednesday night when he became disoriented. He was taken to the Elmhurst hospital and died there at 9:23 p.m., Mr. Sosa said.