The American Psychiatric Association and the American Academy of Psychiatry submitted a request Wednesday to become parties in the case, KTAR-TV, Tucson, reported.
The groups say they want to offer advice on whether Loughner should be forced to take psychotropic drugs for what doctors say is schizophrenia at the Missouri prison facility where he is being held.
In May a federal judge declared Loughner unfit to stand trial for the shootings that killed six people and injured 13 including Giffords at an outdoor constituent meeting in Tucson organized by Giffords' office.
Loughner was sent to a federal prison in Springfield, Mo., for four months of treatment.
The judge has said he will reconsider in late September if the treatment has restored Loughner's competency to stand trial.