MLB officials and the MLB Players Association agreed to a series of revisions to the Joint Drug Prevention and Treatment Program.
Among the changes announced Thursday were increases in the number of random tests, but in season and in the off-season, and the addition of human-growth hormone blood testing during the off-season and Spring Training.
Officials said "reasonable cause" would also be reason for an HGH test. The parties said they were looking into adding such testing during the season.
Other changes alter the program's collection procedures and appeals.
Officials will also be allowed to be made public the specific substance found in a positive drug test that results in discipline.
More than 45 performance-enhancing substances and stimulants have been added to the list of prohibited substances since the current program began four years ago.
"These modifications to expand upon the comprehensive nature of our program are consistent with our efforts to ensure we are running the highest quality drug testing in professional sports," said Rob Manfred, MLB's executive vice president for economics and league affairs. "This agreement is a reflection of our commitment to monitoring our program and making upgrades in all possible areas in order to best serve our game."