A mum in the US has confessed to injecting her son with her own blood, after she was caught on camera by hospital staff.

Elizabeth Malone, 28, was with her five-year-old son in Virginia when the incident occurred.

WJLA reports the mother brought her son to Inova Fairfax Hospital seven times, raising the suspicions of staff.

Her son is disabled and unable to speak.

Hospital staff became suspicious of the mum. (Fairfax County)

During one of those two visits, the boy was bleeding.

The mother-of-three later admitted to placing blood in her son's nose and mouth.

A camera was set up in the hospital room which captured the offence. Malone used hospital medical supplies to draw blood from her right arm and inject it into her son, police allege.

Police watched the video and arrested Malone. (Fairfax County)

The mother later said she committed the offence so hospital staff would ‘respond faster’.

Prosecutors claimed the boy suffered infections and high fevers following the injection.

Malone has pleaded guilty to child abuse and will be sentenced in July.

When confronted by police the mum admitted to the offence. (Fairfax County)

Since his mother’s arrest, prosecutors say the boy’s condition has improved and he is once again able to attend school.