The rapper rose to fame as a member of Big Bang.
T.O.P. is recovering after a suspected drug overdose.
The 29-year-old rapper and member of Big Bang, one of the world's most successful boy bands, was reportedly found unconscious while performing mandatory military service as a policeman on Tuesday.
The singer's medical team told the Korea Herald that he was suspected to have overdosed on benzodiazepine, a range of prescription tranquilizers used to treat anxiety.
"When T.O.P. was brought into the hospital he was in a state of stupor and deep drowsiness and only responded to very strong stimulations. His blood pressure and heartbeat were at an extremely high level," the doctors said of T.O.P., whose real name is Choi Seung-hyun. "He is still not breathing properly and is recovering. We are currently attempting to treat him but he’s in an unresponsive state."
Shortly before his hospitalization, T.O.P. was transferred from his compulsory service posting at a police station in Gangnam to another station, after he was rumored to have smoked marijuana on several occasions. The drug is illegal in South Korea.
"I deserve punishment for hurting the members, agency, public, fans and family," T.O.P. said in a statement released by his entertainment agency, YG, at the time. "I'll regret this for tens of thousands of years."