"He was admitted in the afternoon (yesterday). He suffered a minor brain haemorrhage after he fell down at his home," said the doctor on condition of anonymity.
The 76-year-old Congress leader from Kerala was the defence minister during the UPA government.
He served as the defence minister for more than seven years, the longest for an Indian defence minister.
Earlier this month, he had criticised the Centre for not accommodating the Rohingya and cited the example of former prime minister Indira Gandhi who "insisted on protecting" refugees from Bangladesh.
"When more than one crore refugees came to India from Bangladesh in the 70s, former prime minister Indira Gandhi insisted on protecting them by disregarding the mighty seventh fleet of the US," Antony had said, speaking at the launch of the Kerala Union of Working Journalists, Delhi.