Former Congress president Sonia Gandhi was admitted to Ganga Ram Hospital in New Delhi on Wednesday for routine check-up, sources said.
Her daughter Priyanka Gandhi Vadra accompanied her to the hospital, they said.
According to them, Sonia Gandhi has been suffering from a respiratory infection.
Sources added that Sonia Gandhi has been unwell since Tuesday which is why Rahul Gandhi and Priyanka Gandhi Vadra had returned to Delhi after walking seven kilometres in the Bharat Jodo Yatra that entered Uttar Pradesh on Tuesday evening.
The Congress' Bharat Jodo Yatra resumed its journey at 6 am on Wednesday after halting for the night at Mavikalan in Uttar Pradesh's Baghpat.
Priyanka Gandhi did not, however, join Rahul Gandhi at the yatra's resumption. She is likely to join after noon, party sources said.