"Medically at present, there is no need to panic. Dr Mandela had undergone routine tests for a respiratory infection. Dr Mandela is in high spirits and has been visited by his family and friends," Surgeon-General Vijaynand Ramlakan said.
Mandela, 92, was admitted to Milpark Hospital on Thursday.
Ramlakan said the former South African president had recently developed an acute respiratory infection for which he has received treatment and has responded very well.
"He will be monitored very closely. The family will make arrangements to take him (Mandela) to his home in Houghton for home-based care equal to what he received in hospital," he said.
Ramlakan pointed out that Mandela had contracted tuberculosis while imprisoned on Robben Island for 27 years and had been previously treated for this.
"(Mandela) surprises us on a daily basis with his recovery," the surgeon-general said, adding that similar checkups in the past had not generated the amount of public interest that this one has.
"His amazing positive attitude allows him to cope with the difficulties of old age with the greatest of graces. When you are 92 years old, it is very different to being 19 years old," he said.
The government did not release specific information about the reason for Mandela's hospitalisation, or why he remained there overnight. Acting president Kgalema Motlanthe conceded that in retrospect, the matter could have been handled better.
President Jacon Zuma was away in Davos at the World Economic Forum. Echoing his views, Ramlakan said in future there would be regular bulletins if the need arises.
"He is also not as mobile as before and over the past few years has had to be assisted with movement," he said.
Mandela, who was jailed for 27 years for his fight against apartheid, became South Africa's first black president in 1994 and stepped down after serving one term in 1999. Mandela retired from public life in 2004.