Dravida Munnetra Kazhagam (DMK) chief Karunanidhi is recovering well and will be discharged after completion of course of antibiotics.
The Kauvery Hospital where Karunanidhi is undergoing treatment said in a statement.
The former chief minister was earlier on December 15 admitted to the hospital for the second time in the last three weeks.
He was first admitted to the same hospital on December 1 for optimisation of nutrition and hydration and was discharged after he improved substantially.
The hospital had earlier issued a statement, saying Karunanidhi was readmitted with breathing difficulty due to throat and lung infection, adding that he was stable and being treated.