E.E.U.U. - National League MVP Ryan Braun's failed drug test was the result of medication he was taking for a "private medical issue," a source told TMZ Monday.

The Milwaukee Brewers outfielder tested positive for a substance that is banned under Major League Baseball's drug policy. The result was announced Dec. 10, but Braun said he had known about the positive test since late October.

Last week, a source told FOX Sports that the test result was not linked to a performance-enhancing drug. The original report from ESPN stated the 28-year-old Braun had elevated levels of testosterone.

The specific issue for which Braun was taking the medication is unclear, but the source told TMZ the medication contained the substances which triggered the failed test.

Immediately after the test result was announced, a spokesman for Braun called the situation "highly unusual" and said the four-time All-Star was confident he would be exonerated.

Braun's .332 batting average in 2011 was second in the National League, and Braun led the league in slugging percentage at .597 and on-base plus slugging percentage (OPS) at .994.