Officials said he was taken to hospital overnight for a "long-standing abdominal complaint" which needed "proper specialist medical attention".
A government spokesman said the former leader was "in good spirits and well".
The 93-year-old statesman and anti-apartheid icon has suffered declining health in recent years.
In a statement, he asked for Mr Mandela and his family to be given privacy.
Mandela retired from public life eight years ago - his last public appearance was at the World Cup in South Africa in 2010.
The Nobel Peace Prize winner is affectionately known in South Africa as Mandiba.
He spent 27 years in prison for his actions against the apartheid regime before being released in 1990.
In 1994, he became South Africa's first black president, stepping down in 1999 after one term.