Most of those injured at the Uribana prison in Lara state suffered gunshot wounds, said the hospital official, Ruy Medina.
He called the death toll "alarming," saying it was based solely on bodies brought to the hospital.
Medina said the inmates began arriving at the hospital shortly before midday, and that 14 of the injured had wounds severe enough to require surgery.
Iris Varela, the government minister responsible for Venezuela's jails and prisons, said the riot was set off after inmates rebelled when prison authorities launched a sweep of the facility in search of illicit weapons.
Varela had said earlier in the day that there was an "undetermined number" of casualties from the melee.
Venezuela is infamous for the lamentable state of its prisons, especially for their overcrowding, which is among the worst in Latin America.
While the country's prisons have been built to house 14,000 inmates, there are almost 50,000 prisoners behind bars.