Ahmadinejad, who was elected president in 2005, has not said whether he will seek a second term in the June 2009 presidential race but is widely expected to run.
Asked on state television about his health, he said: "We are human like all others and catch colds. No, I am not ill."
A member of parliament, Mohammad Ismail Kowsari, told the official news agency IRNA on Saturday that some websites had spread rumors about Ahmadinejad's health and had suggested it could harm his chances of running for president again.
"Any human might come down with weakness as a result of workload and pressure. This is something natural," Kowsari said, adding that those who used such a "psychological ploy" of spreading rumours would fail.
The president has been criticized for surging inflation which has hit 29 percent and now faces the added challenge of tumbling oil prices, which are cutting into Iran's main source of revenue.
(Reporting by Hossein Jaseb, writing by Edmund Blair; editing by Elizabeth Piper)
