"I met the Chairman, Apollo Hospitals. The state Health Minister was also there. I was told that the Chief Minister was improving and recovering fast," he told reporters.
The 68-year-old AIADMK supremo was admitted to the hospital on September 22 after she complained of fever and dehydration.
The hospital later said she was being treated for an infection.
"On behalf of the people of Kerala, I pray for her speedy recovery," Chennithala said.
An expert team of doctors from All India Institute of Medical Sciences (AIIMS) and a UK-based specialist are continuously monitoring the health condition of Jayalalithaa.