The 93-year-old leader has been ailing since last year and was being treated at his Gopalapuram residence in Chennai.
The former chief minister "has been admitted for a minor procedure - change of (Percutaneous endoscopic gastronomy) PEG tube. He will be discharged from the hospital later today," Kauvery Hospital Executive Director S Aravindan said in a statement.
On December 15 last year, Mr Karunanidhi was admitted to a hospital in Chennai for a week due to breathing difficulty caused by throat and lung infections. On December 16, he underwent tracheostomy to optimise breathing, following which doctors advised him "complete rest and restriction of visitors."
Though active for his age, the veteran DMK leader is not seen regularly in public and has been reacting to key issues and developments through his statements.