The problem was detected on the 35-year-old during a routine medical check up at his current side Gremio earlier this week.
Lucas rejoined boyhood club Gremio this summer after five years with Lazio in Italy and scored three goals in 18 appearances as promotion was secured from Serie B to the Brazilian top flight.
"The Medical Department of Gremio communicates that, after alterations were diagnosed in one of the routine pre-season exams of the athlete Lucas Leiva, he was submitted to complementary evaluations and referred to specialists," the statement read.
"Once the evaluations were completed, conducted by doctors Leandro Zimerman and Ricardo Stein, it was determined that the athlete should stay away from high-performance physical activities for a period of two to three months, during which he will be accompanied, monitored and guided by the club's medical team and the aforementioned specialists.
"After this period, Lucas Leiva will undergo further examinations and evaluations to determine the evolution of his clinical condition."
Lucas, who won 24 caps for the Brazil national team, earned cult hero status at Liverpool during a ten-year stay at Anfield between 2007 and 2017.
