Forston, originally an undrafted free agent out of Miami in 2012, has played limited snaps as a reserve interior defensive lineman this season.
The Patriots needed to clear room on the roster to sign free-agent tight end D.J. Williams, as was reported earlier Tuesday.
Forston is the second defensive tackle the Patriots have lost today, as practice squad player A.J. Francis was signed to the Dolphins' active roster.
Forston, who has practice-squad eligibility, is now subject to the league's waiver system. If he clears, he could be re-signed to the team's practice squad.