A woman was arrested north of Sydney on Tuesday after allegedly poisoning her nine-year-old daughter to the point the child was left fighting for her life.

It is suspected by investigators to be a case of the psychological illness Munchausen syndrome, where people either harm themselves or loved ones to gain attention.

Child abuse detectives were called in to investigate after the girl was admitted to a Hunter Valley hospital with life- threatening renal failure and other serious medical conditions, local media reported.

Police alleged the girl was given a contaminated substance intravenously that made her unwell. She has since recovered.

Police also alleged the child was given tablets that caused medical complications in 2014.

The girl's mother, 42, was arrested and charged with using poison to endanger life or inflict grievous bodily harm, and assault causing actual bodily harm.

She was granted bail on Tuesday afternoon.