Diego Maradona is set to undergo surgery because of possible bleeding on his brain.
The 1986 World Cup champion's personal doctor said Maradona had an accumulation of blood on his brain.
The neurologist said the problem was likely to have been caused by an accident, but Maradona does not remember such an event.
"He has a subdural hematoma," Leopoldo Luque told journalists.
"We will do it [the surgery] today."
Maradona was admitted to a private hospital with signs of depression on Monday, three days after his 60th birthday.
Dr Luque said Maradona, whose "Hand of God" goal against England in 1986 is among the most controversial in World Cup history, had felt depressed for about a week and refused to eat before arriving at the clinic.
"He is anaemic and a bit dehydrated. We have to correct that," Dr Luque said.
He added Maradona would be transferred to Olivos Clinic in Buenos Aires province.
Maradona, who is widely considered to be one of the greatest players of all time, coaches local club Gimnasia y Esgrima.
Maradona turned 60 on Friday and showed up that night for Gimnasia's national championship match against Patronato, which his team won 3-0. He left before the end of the first half, raising questions about his health.
Earlier on Tuesday, the former star for Barcelona, Napoli and Boca Juniors had said he felt better.
Dozens of fans of Gimnasia y Esgrima have converged on the hospital since Monday evening, waving flags and holding posters with messages of support for Maradona.
"What we want the most is for Diego to get out of all this, said one of the fans outside the hospital, Diego Bermudez, 41.
"He can, he is the greatest, the greatest in the world."