94-year-old Mandela, who was South Africa's first black President, was hospitalised yesterday "to undergo tests," President Jacob Zuma's office said in a statement.
The Nobel Peace Prize laureate "is doing well and there is no cause for alarm," the statement said.
"As said before, former President Mandela will receive medical attention from time to time which is consistent with his age," Presidential Spokesperson Mac Maharaj was quoted as saying by News24.
In January 2011, Mandela was treated for a serious chest infection. A year later, he underwent a diagnostic procedure for an abdominal problem.
Mandela spent over two decades in prison under the white minority apartheid regime.
He become South Africa's first black president in 1994.