Singh, a senior leader of the opposition Congress, is currently a Member of Parliament in the Rajya Sabha from Rajasthan. He was the prime minister between 2004 and 2014. In 2009, Singh underwent successful coronary bypass surgery at the AIIMS.
The former PM, 87, was admitted after he suffered a reaction to a new medication and developed fever, according to news agency PTI.
He was admitted under Dr Nitish Naik, a professor of cardiology at the All India Institute of Medical Sciences (AIIMS), around 8.45 pm, according to reports.
The leader was first taken to the hospital’s cardiac care unit, or ICU for heart patients and later shifted to a private room where he was kept under close observation.
After he got admitted a sample was taken to check if he was infected by coronavirus but he had tested negative. The former PM, who has a heart ailment, is the first leader to serve two complete terms of five years each since Jawaharlal Nehru.
As the news came out, a number of leaders expressed concern over his health and wished him a speedy recovery.
The Congress leader has last appeared in public on May 6, when he took part in a video conference along with acting Congress president Sonia Gandhi and Congress chief ministers.