Stanford spent nearly nine months this year being treated in a North Carolina federal prison hospital for an anti-anxiety drug addiction he developed while jailed in Houston.
Stanford's attorneys have said his addiction as well as a brain injury he suffered in a jail fight left him unable to think clearly or help in his own defense.
In court documents filed Thursday, prosecutors say prison doctors have found Stanford's mental capacity to be normal.
Stanford is accused of bilking investors out of $7 billion in a massive Ponzi scheme.
A competency hearing is set for Tuesday. Stanford's trial is set for Jan. 23.