Hope Solo tested positive for a banned substance found in her pre-menstrual medication and received a public warning from the U.S. Anti-Doping Agency on Monday.
Solo, 30, tested positive for the banned substance canrenone as the result of an out-of-competition urine sample collected June 15.
USADA said she was taking the medication in a "therapeutic dose under the care of a physician." Canrenone is classified as a specified substance, meaning that its presence in an athlete's sample can result in a reduced sanction.
"I took a medication prescribed by my personal doctor for pre-menstrual purposes that I did not know contained a diuretic," Solo said in a statement. "Once informed of this fact, I immediately cooperated with USADA and shared with them everything they needed to properly conclude that I made an honest mistake, and that the medication did not enhance my performance in any way."
U.S. Soccer said in a statement that it fully supported Solo's "clarification" of the test result.
Solo is the starting goalkeeper for the U.S. women's soccer team that will play in the Olympics. The Americans' first game is July 25 against France.