Zambia's President Edgar Lungu collapsed on the podium while presiding over a Women's Day celebration in Lusaka - less than two months after taking over from a leader who died in office.
Lungu was rushed to a military hospital on Sunday, but the president's office later issued a statement saying he had been treated for malaria and there was no need for concern.
"I am feeling much better and have been told I have high levels of fatigue and should take some rest," Lungu said in the statement.
"There is nothing to worry about."
Lungu came to power in January after the death in office of President Michael Sata in October.
Rumours that Sata was ill had circulated widely before his death, but were always denied by the government.
Sata was Zambia's second leader to die in office in six years, sparking calls for presidential aspirants to undergo medical checks to guarantee they are fit.
Lungu, who fell after standing for some 20 minutes during the ceremony, is rumoured to have diabetes, the AFP news agency reported.
Presidential spokesman Amos Chanda said doctors at the military hospital had conducted comprehensive medical checks and said Lungu's results were good.