Singh, 87, was taken to All India Institute Of Medical Sciences (AIIMS) in New Delhi on Sunday and was under observation in the cardio-thoracic ward where he was being treated by a cardiologist. He is currently not in critical condition and away from the intensive care unit (ICU) of the hospital in a private room.
Singh served as the 13th prime minister of India from 2004 to 2014, and he currently serves in the Upper House of Parliament.
The former prime minister underwent a heart-bypass surgery in 2009 at AIIMS.
There is so far no indication if Singh is suffering from the coronavirus, though India has been one of nations hit hard by the outbreak. Medical experts have suggested advanced age and pre-existing conditions affecting the immune system can make a virus such as Covid-19 far more deadly.
India has counted over 2,000 deaths from the pandemic and over 60,000 confirmed cases. It went into a national lockdown at the end of March, which has been in the process of being lifted through phases in the last few weeks.