Medics at a Sao Paulo hospital said Socrates, widely regarded as one of the greatest midfielders of all time, remained on life support on Saturday.
He has been in a critical condition with an intestinal infection since being admitted to intensive care on Friday night.
Socrates, who played in two World Cups, won 60 caps for his country between 1979 and 1986, scoring 22 goals.
The Brazilian, whose full name is Socrates Brasileiro Sampaio de Sousa Vieira de Oliveira, was taken to the Albert Einstein Hospital in Sao Paolo with food poisoning on Friday, his wife said.
A hospital statement said the former footballer was "in a critical condition due to a septic shock of intestinal origin".
It added he was breathing with a ventilator and using a dialysis machine.
Socrates was hospitalised twice in August and September this year with bleeding in his digestive tract.
After these incidents he admitted he had problems with alcohol, and especially so during his playing career. He is also well known for his smoking habit.
In a recent television interview, Socrates said he had considered alcohol his "companion" but believed its regular use did not affect his performance on the field.
"Alcohol did not affect my career, in part because I never had the physical build to play this game," he said.
"Soccer became my profession only when I was already 24. I was too thin, and when I was young, I did not have the opportunity to prepare myself physically for the sport."
FACTFILE
Born on 19 February 1954 in Belem do Para, Brazil
Rated as one of the greatest midfielders of all-time
At 6ft 4in tall he was known for his physical strength, as well as two-footed vision and skill
Played for Botafogo and Corinthians in Brazil before a one-season spell at Fiorentina
Saw out his career with Flamengo and Santos before retiring in 1989 aged 35
In 2004 aged 50 Socrates made an appearance as sub for Garforth Town in the Northern Counties League after a one-off deal to become player-coach
