The deceased, Sharath Prabhu, was a student of PG medicine at GTB Hospital.
He was staying in the flat with two others and around 11.30 pm last night the trio had dinner, police said.
Mr Prabhu was found unconscious outside the washroom of the apartment around 7 am by his flatmates, who rushed him to a hospital where he was declared brought dead.
His flatmates are being questioned. He belongs to Coimbatore and was staying in Delhi since May 2017.
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.