A Congress spokesman expressed the hope that she would rejoin "parliament proceedings at the earliest".
"She is perfectly all right. She is stable," Bhakta Charan Das told the media.
The Congress president did not attend the Lok Sabha Tuesday.
Gandhi, 66, was admitted to the All India Institute of Medical Sciences (AIIMS) late Monday after she felt uneasy in the Lok Sabha when the house was debating the food security bill.
After noting that there was "nothing abnormal" with her condition and that all her health parameters were "perfect", the doctors decided to keep her under observation and discharged her around 1.30 a.m. Tuesday.
An AIIMS statement said Gandhi had viral fever and "felt some degree of uneasiness" while in parliament.
It said a team of doctors led by AIIMS director R.C. Deka examined her. "All the tests were found normal and she did not require any definitive treatment."
It added that Gandhi was "happy on the outcome of the test reports and the care provided by doctors, nurses and other staff of AIIMS".
On Tuesday, Health Minister Ghulam Nabi Azad told IANS: "She is doing fine and is resting."
Prior to the AIIMS statement, there was some confusion about the nature of her ailment.
While Azad and party leader Janardan Dwivedi said Gandhi was suffering from "common cold and headache" and had taken some medicines that did not suit her, Das said "she had minor viral fever and a headache".
"When I walked up to her in the house, from her facial expressions I felt she was not well," recounted Das.
Another Congress leader, who did not wish to be identified by name, however, said Gandhi complained of chest pain -- before the Lok Sabha took for voting numerous amendments to the bill.
Some MPs had noted a slight shivering of hands as Gandhi read her speech in the Lok Sabha Monday.
Accompanied by central minister Kumari Selja and her son and Congress vice president Rahul Gandhi, Gandhi was rushed to AIIMS Monday night.
The Congress attacked Gujarat Chief Minister Narendra Modi for tweeting that "she should have been taken to hospital in an ambulance".
"In a civilized world people should not do politics over somebody's health. There are facilities in parliament but it was a private affair," said Das.
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