The former footballer, Ronaldo Nazário de Lima, was admitted into the Hospital de Can Misses in Ibiza last Friday.
The 41-year-old World Cup victor was diagnosed after falling ill on Friday and was rushed to the Can Misses Hospital on the Spanish island of Ibiza.
Later that night, he requested transfer to the Nuestra Señora del Rosario hospital owned by Policlinica, a private health-care company.
Hospital sources have said he is still in intensive care but making good progress.
Staff at Can Misses Hospital said they were unable to give out any information for "data protection reasons". Throughout a prosperous career, he scored 62 goals in 98 global appearances for Brazil.
Ronaldo, who rose to global fame in the 1990s, and played for various clubs, including Barcelona, Inter Milan and AC Milan, is widely considered to be one of the best football players of all time.
Ronaldo then took to his own official account on Sunday to reassure supporters and those who had sent him well-wishes, however, while confirming the trip to hospital was true.
He is believed to have arrived in Ibiza for a summer break a few days ago. Tissue swells, and it can cause coughing and breathing difficulties.
Ronaldo finished his career with an impressive 414 goals, 62 of which came in just 98 appearances for the Brazilian national side.
He finished his career with 12 goals in the World Cup finals, tying with Pele for the all-time record.
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