17-year-old Afzal allegedly tried to molest the woman and when he failed to do so, he poisoned her, SHO Jagdishpur Shiv Muni Yadav said.
The woman was admitted to Community Health Centre Jagdishpur, but after her serious condition doctors referred her to Trauma Centre in Lucknow, police added.
An FIR has been lodged against the absconding accused with Jagdishpur police.
Police is looking seriously into the matter, they said.
