South African media reports say he was complaining of chest pains.
Department of Corrections spokesman Logan Maistry told The Associated Press that Pistorius was taken to the hospital today and was expected to return to the prison later the same day.
However, Maistry said Pistorius will now stay overnight in the hospital "for observation."
Maistry declined to give details of Pistorius' medical complaint citing department rules preventing the divulging of information on offenders.
Pistorius, the double-amputee Olympic runner and multiple Paralympic champion, is serving a six-year jail term for murder in the shooting death of girlfriend Reeva Steenkamp in 2013.