NFL player representatives could vote Tuesday on proposed changes to the sport’s drug policies that, if ratified, would include players being blood-tested for human growth hormone, multiple people familiar with the deliberations between the league and the players’ union said Monday night.

One of those people said the potential vote of the players’ union representatives from the 32 NFL teams is “not a guaranteed ‘yes’ vote.”

Another said the player representatives will speak via conference call Tuesday and whether or not a vote takes place “depends on the league” and the state of the negotiations with the NFL.

The possible vote would come after representatives of the league and the union met Monday. The two sides did not reach an agreement on all issues, according to those people with knowledge of the negotiations, but came close enough to doing so for the NFL Players Association to schedule Tuesday’s conference call and potential vote.

The changes, if ratified, also could include an increased threshold for what constitutes a positive test for marijuana, and a positive test for amphetamines being covered under the sport’s substance abuse policy instead of under its performance-enhancing drugs policy. Some current suspensions, including those of wide receivers Josh Gordon of the Cleveland Browns and Wes Welker of the Denver Broncos, could be reduced if the changes are enacted.

The league and union agreed as part of their 2011 labor deal for players to be blood-tested for HGH, which already is on the NFL’s list of banned performance-enhancing substances. But disagreements over the details of the program have kept the testing on hold for three entire seasons.

The proposed changes would give the players a system of neutral arbitration to resolve appeals of drug-related suspensions, instead of NFL Commissioner Roger Goodell or a person designated by him deciding all such appeals. One of the final disagreements between the league and union was the NFL’s desire for the commissioner to retain authority to resolve appeals of discipline resulting not from a positive test, but from a violation of the law or other evidence of a violation of the drug policy. The exact mechanism by which the two sides would resolve that issue was not immediately clear.

The modifications to the drug policies also could result in increased penalties for players convicted of driving under the influence. The league has been seeking a two-game suspension for a player convicted of DUI. The NFL also sought during the negotiations to have a player arrested for DUI subject to a one-game de-activation with pay before the legal process would play out. The union resisted that proposal, and it was not known if it was abandoned by the league.

Gordon and Welker have served one game of their suspensions. Gordon is suspended for the entire season for a violation of the substance abuse policy, reportedly for a positive marijuana test. The proposed changes apparently would raise the threshold of what would constitute a positive test for marijuana above the level at which Gordon tested.

Welker was suspended for four games for testing positive for a banned performance-enhancing substance, reportedly amphetamines. The proposed changes apparently would have amphetamines being covered by the substance abuse policy rather than by the performance-enhancing drugs policy, and a first violation of that policy would not result in a suspension.