Volquez said in a statement he received a prescription in the Dominican Republic as part of treatment to start a family with his wife. He said the drug was banned by Major League Baseball.
"As a result, I tested positive when I reported to spring training," he said. "Although I understand that I must accept responsibility for this mistake and have chosen not to challenge my suspension, I want to assure everyone that this was an isolated incident involving my genuine effort to treat a common medical issue."
Volquez became the first player suspended under the major league drug program since Manny Ramirez of the Los Angeles Dodgers was penalized 50 games last May.
Volquez's suspension starts Wednesday. The 26-year-old right-hander was already out of action — he's recovering from reconstructive surgery on his elbow and was expected to rejoin the Reds around midseason.
Barring Reds rainouts, Volquez could play starting June 15 against the Dodgers.
An All-Star in 2008 when he went 17-6 with a 3.21 ERA for the Reds, Volquez was 4-2 with a 4.35 ERA last season before feeling pain in his arm in June. He twice went on the disabled list, the first time with back spasms and then with the elbow injury that finished his season.
"The Reds fully support Major League Baseball's drug policy and its penalties. The organization does not condone in any way the use of drugs not sanctioned by MLB's medical staff," the team said in a statement before Tuesday night's game against the Dodgers.
MLB's labor contract does not allow it to release which drug caused the positive test. A list of drugs that trigger positives is released after each season, without identifying which player used it.
MLB and the players' union repeatedly warn players not to use any substance without guidance from doctors or trainers who are aware of the banned list.
"I was not trying in any way to gain an advantage in my baseball career," Volquez said in his statement. "I am embarrassed by this whole situation and apologize to my family, friends, fans, teammates, and the entire Reds organization for being a distraction and for causing them any difficulty.
"I simply want to accept the consequences, learn from the mistake, and continue to strive to be the best person and baseball player I can be," he said.
Ramirez was suspended after turning over to MLB a prescription for a banned female fertility drug.
Volquez was the first player suspended for a positive test under the big league program since San Francisco pitcher Kelvin Pichardo on March 23, 2009.
The only other players suspended under the major league program last year were Yankees pitcher Sergio Mitre and Philadelphia pitcher J.C. Romero, both in January 2009.
There have been 16 suspensions this year under the minor league drug program.
Volquez made his major league debut with Texas in 2005. He was traded in December 2007 to the Reds for outfielder Josh Hamilton. Both players were at the 2008 All-Star game at Yankee Stadium.