Edelman did not acknowledge violating the league's policy on performance-enhancing substances in the posting on his Instagram account.
"I am very sorry -- I don't know what happened," Edelman wrote on the posting. "I've taken many, many tests obviously over the course of my career, and nothing like this has ever happened. I apologize to the Kraft family, my coaches, teammates and fans.
"As this matter is being appealed, I can't say anymore but no matter what, I will be ready to play and pursue another championship with our team and for Patriots fans around the world."
Edelman, who missed the entire 2017 season after suffering a torn ACL in an exhibition contest in August, is appealing the suspension.
If the punishment is upheld by the NFL, Edelmen will miss the Patriots' season opener against the Houston Texans (Sept. 9), road games versus the Jacksonville Jaguars (Sept. 16) and Detroit Lions (Sept. 23), as well as a home tilt against the Miami Dolphins (Sept. 30).
Edelman, 32, has been a favorite target of quarterback Tom Brady when healthy over the last several seasons. He caught 98 passes for a career-high 1,106 yards in 2016.
A converted college quarterback who was a seventh-round draft pick of New England in 2009, Edelman has recorded 425 receptions for 4,540 yards and 24 touchdowns in 103 career games.
New England added Jordan Matthews and Cordarrelle Patterson this offseason and selected Braxton Berrios in the sixth round of the 2018 NFL Draft to join a depth chart that includes Chris Hogan, Phillip Dorsett, Malcolm Mitchell and Kenny Britt.
Mitchell, like Edelman, missed the entire 2017 season and has been limited to conditioning drills during the team's offseason program.