The NFL announced Bell's three-game suspension Friday, saying the former Pro Bowler violated the league's substance-abuse policy.
Bell's suspension was reduced from its initial length of four games as a result of a negotiated settlement between the NFL and the players' union, a source told ESPN's Dan Graziano.
Also, as part of the settlement, Bell remains in his current stage of the NFL's drug program rather than advancing to the next one, the source told Graziano. The missed drug tests were found to be the result of a travel issue, and Bell did not inform the tester of his travel plans, according to the source.
In a video that was removed from his Twitter feed shortly after posting, Bell apologized to his teammates and to Steelers fans.
"I put the blame on myself," Bell said. "After this whole situation is done, you'll get a better person and a better player out of it."
Bell also posted an apology on his Instagram account that he later deleted.
"I'm not the perfect person,'' Bell said. "I'm not going to say I act like a perfect person. I make mistakes. I want to apologize for everything I put you guys through the last couple years. It's been a frustrating run for you. It's been a frustrating run for me.''
Steelers general manager Kevin Colbert said in a statement that the team is "disappointed" in Bell, who was suspended two games last season following an August 2014 arrest for marijuana possession and a charge of DUI in August 2014 in the Pittsburgh area.
"We will continue to support Le'Veon, but we acknowledge this mistake has put the team in an unfortunate position," Colbert said. "We will continue to work with Le'Veon to help him eliminate distractions in his life so he can reach his full potential as a member of our community as well as a player for the Pittsburgh Steelers."
Bell, who practiced throughout training camp coming off reconstructive knee surgery, had faced the cloud of an NFL suspension for the second consecutive year. He sat out the first two games of the 2015 season as punishment for his arrest in August 2014 on DUI and marijuana possession charges following a traffic stop. Bell was originally suspended three games before it was reduced on appeal.
He declined comment on the appeal process during training camp but said Tuesday he appreciated the support from teammates who took the wait-and-see approach.
Offensive coordinator Todd Haley, for example, called Bell an "energy giver" who endeared himself to the team quickly.
There was a sense of optimism from the Steelers during training camp, with one team source saying Bell's story for missing tests was much better than his changing his cellphone number, a popular rumor that circulated online.
Steelers coach Mike Tomlin said Tuesday that Bell's looming appeal hadn't affected his game plan. Running back DeAngelo Williams -- who last season rushed for 907 yards and 11 touchdowns in Bell's absence -- is set to miss his second consecutive preseason game next weekend. Third-stringer Fitzgerald Toussaint is expected to take the first-team reps.
Bell will be eligible to return to the active roster Sept. 26, before the team's Week 4 home game against Kansas City. He will miss the season opener at Washington, the first home game against Cincinnati and the next game at Philadelphia.
Bell said in the Instagram post he never purposefully missed or failed any drug test.
"They tried to test me in December and January and I missed those tests," Bell said. "I couldn't get to the facility and get tested. They couldn't come to me and get tested. That's on me. I put blame on myself."
Bell added that he was supposed to get tested again in April and overslept.
"I ended up missing the test," Bell said. "I was sleeping and that's on me. I can't blame anybody else for missing my test. I just want everybody to understand I never tried to purposefully avoid or evade any test."
The 24-year-old All-Pro running back is entering the final season of his rookie contract.
Since 2013, Bell has averaged 119 yards from scrimmage per game, the NFL's best among running backs.
Bell finished second in the league with 1,361 yards rushing and 2,215 all-purpose rushing and receiving yards in 2014. He rushed for 556 yards and three touchdowns and caught 24 passes for 136 yards in 2015 before tearing the MCL and PCL in his right knee when Cincinnati linebacker Vontaze Burfict dragged him to the ground in November.
Bell hasn't played in a preseason game, but has fully participated in training camp practices, showing the ability to take hits and sharply cut on his injured knee. Bell will be able to participate in training camp practices and the final two preseason games before the suspension begins.
Pittsburgh finished third in total yards and fourth in scoring in 2015 while going 11-7 and losing to Denver in the AFC divisional round. The Steelers are already without wide receiver Martavis Bryant, who will miss the entire season after he was suspended in March for a second violation of the league's substance abuse policy.
Williams will fill in as the team's starting running back with Bell out of the lineup.
ESPN's Adam Schefter and Jeremy Fowler and The Associated Press contributed to this report.