Jihad Diyab, a 45-year-old Syrian, had been taken to Hospital de Clinicas in Montevideo, a government intermediary with former inmates from the US military prison told AFP.
"Staff spoke with him for three hours trying to have him receive assistance and accept testing, but it was impossible. He also spoke with some friends, but there was no way, it was impossible," hospital director Raquel Balleste told El Observador newspaper.
"We think that he must be admitted but must respect his autonomy and his rights."
It was the second time his week that Diyab was hospitalised after launching a hunger strike about three weeks ago to press his demand to be reunited with his family in Turkey.
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On Friday, Diyab told local media that if he died, his death would be the responsibility of "the United States and Uruguay."
Held in Guantanamo for 12 years without charge, Diyab was released in 2014 from the US-run military prison in Cuba to Uruguay along with five other former inmates under an agreement with Washington.
The ex-prisoner has repeatedly shown that he wants out of Uruguay.
He fled the country and turned up in Venezuela, where he appeared at the Uruguayan consulate on July 26 seeking help reuniting with his family in Turkey.
In Venezuela, Diyab was jailed at the headquarters of the secret police, who prevented him from receiving visitors, including activists following his case and his US-based lawyer, Jon Eisenberg.
He was sent back to Uruguay on August 30.
Diyab insists he cannot financially support his family in Turkey while living in Uruguay.
