A 17-year-old boy from Adelaide's south who allegedly gave false medical treatment to a girl who had fallen off a scooter has been charged by police.

Police say the boy purported to be medically qualified when he examined the 12-year-old girl at Edwardstown on Monday and administered a prescription drug.

He has been charged with several offences, including aggravated assault and identity theft.

The boy has been given bail to appear in the Adelaide Youth Court at a later date.