Pistorius, 30, is serving a six-year jail term for murdering his girlfriend Reeva Steenkamp, a model and law graduate, in his Pretoria house in 2013.
The “Blade Runner”, as he was known, has always maintained that he mistook Steenkamp for an intruder when he fired four high-calibre bullets through a locked toilet cubicle.
“This morning he went for a medical examination and he was scheduled to return back (to jail), but he will now be kept overnight for observation,” Logan Maistry, spokesman for the department of correctional services, told AFP.
Maistry added that the department would not release details on Pistorius’s medical condition.
The News24 website said Pistorius was taken from Atteridgeville prison in Pretoria to hospital in an ambulance after complaining of chest pains.
The year before he killed Steenkamp, Pistorius became the first double-amputee to race at the Olympic level when he appeared at the London 2012 games.
While on parole he gave a television interview saying that an “instant fear” drove him to open fire.
|The South African Paralympic gold medallist (right) is serving a six year sentence for murdering model Reeva Steenkamp (left) on Valentine's Day 2013|
Pistorius testified that he killed Steenkamp by mistake, thinking there was an intruder hiding in the bathroom. Prosecutors said he shot her intentionally after an argument.
The initial manslaughter conviction was upgraded to the more serious offense of murder after an earlier prosecution appeal, leading to a new sentencing.
In August last year, Pistorius received emergency treatment for injuries to his wrists prompting speculation that he had attempted suicide in jail.
The Paralympian denied the injuries were a suicide attempt and claimed he had 'fallen out of his bed' in his cell at Kgosi Mampuru prison in Pretoria.