(Image Credit: Peter Dejong/AP Photo)

Former South African President Nelson Mandela was admitted to the hospital today for a scheduled medical check-up, according to a statement from the South African President's office.

Mandela, 94, is undergoing tests at a Pretoria hospital to "manage existing conditions in line with his age," the statement said. Doctors have said there is no cause for alarm.

In December, the anti-Apartheid activist was hospitalized for 18 days. He was treated for gallstones and a lung infection.

Mandela served as South Africa's first black president from 1994 to 1999.

PHOTOS: Mandela Through the Years

Despite rare public appearances, Mandela, who is credited with changing race relations in South Africa, remains hugely popular in the country.

In November 2012, banknotes featuring Mandela's image were printed and entered into circulation in South Africa.

After enduring nearly three decades of prison, much of it at hard labor in a lime quarry, Mandela emerged as a gentle leader who became South Africa's first black president. He was awarded the Nobel Peace Prize for his leadership in ending apartheid without violence, and later became a global statesman who inspired millions people around the world.