But he denies published reports that he was a multiple offender.
Hernandez was drafted in the fourth round last week, the 113th overall pick in the draft. Hernandez says he was upfront with all of the teams he talked to about the drug test and expressed his regret.
Hernandez set records for a Florida tight end last season with 68 catches and 850 yards receiving while playing with star quarterback Tim Tebow.
He says he's excited about beginning his NFL career and wants to represent the Patriots well.
The Patriots declined to comment.