Nelson Mandela pictured in June 2012
President Zuma's spokesman says there is "no need for panic" as doctors are treating Mr Mandela for a pre-existing condition.
Former South African leader Nelson Mandela has been admitted to hospital for a scheduled medical check-up s.
The latest tests come just months after Mr Mandela, 94, was treated for a lung infection and gallstones.The government said he was in hospital for a "routine test", and a spokesman for the country's president, Jacob Zuma, said there was "no need for panic".
He added that doctors were treating Mr Mandela for a pre-existing condition.
According to a statement from the presidency, he was taken to a hospital in Pretoria.
It said: "Doctors are conducting tests and have thus far indicated that there is no reason for any alarm."
Presidential spokesman Mac Maharaj said: "Former president Nelson Mandela was admitted to hospital in Pretoria this afternoon for a scheduled medical check-up to manage the existing conditions in line with his age."
He appealed for the public to respect the privacy of Mandela and his family.
The Nobel laureate has become increasingly frail and last made a public appearance on a major stage when South Africa hosted the 2010 World Cup soccer tournament.
He has a history of lung problems dating back to when he contracted tuberculosis during his 27 years in prison under South Africa's apartheid regime.