Johannesburg - President Jacob Zuma was admitted to hospital for tests on Saturday, the presidency said.
His spokesperson, Mac Maharaj, said doctors were satisfied with Zuma's condition.
He did not say which hospital the president had been admitted to.
On Friday, the ANC national officials ordered Zuma to take a break.
"Following a gruelling election campaign we found that he needed to rest," the deputy president Cyril Ramaphosa said at the Nehawu special congress in Benoni, on the East Rand.
"He attended the NEC lekgotla this morning [Friday] and was thereafter sent packing to go and rest."
Zuma was scheduled to address the National Education, Health and Allied Workers Union congress, but sent Ramaphosa to deliver his speech.
ANC secretary general Gwede Mantashe told reporters at the ruling party's lekgotla in Irene, outside Pretoria, that the president was exhausted.
He said Zuma was given time to recover before he held a Cabinet lekgotla next week.