Gandhi was admitted to the Army's Research and Referral Hospital here late last night due to high fever.
The 69-year-old Congress chief returned here by a chartered flight close to midnight after she had to abandon the 8-km roadshow in Varanasi midway due to illness.
Gandhi has been shifted to Gangaram Hospital as she had earlier also undergone treatment there, sources said.
Earlier in the day, AICC media cell in-charge Randeep Surjewala had said that she is stable and is recovering under medical supervision.
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The Congress President is overwhelmed by the concern and affection of fellow countrymen and crores of Congressmen and has thanked everyone for their good wishes, he had said.
Congress Vice President Rahul Gandhi and Priyanka Gandhi, were by her side. Her son-in-law Robert Vadra also visited her.
Senior party leader Ghulam Nabi Azad had yesterday said that her condition was "stable" after she suffered a bout of "dehydration, vomited and had fever" in Varanasi.