Solo's prescribed medication is classified as a specified substance by USADA that can result in a reduced sanction.
US national team goalkeeper Hope Solo tested positive for a banned substance found in her pre-menstrual medication and received a public warning for the violation, the US Anti-Doping Agency (USADA) said on Monday.
Solo, 30, tested positive for Canrenone as the result of an out-of-competition urine sample collected on June 15 but will not be ruled out of the July 27-Aug. 12 London Olympics.
The prescribed medication is classified as a specified substance by USADA that 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.
"As someone who believes in clean sport, I am glad to have worked with USADA to resolve this matter and I look forward to representing my country at the 2012 Olympic Games in London."
Solo was the starting goalkeeper for the United States in their run to the gold at the 2008 Olympics and was a standout performer for the US team that reached the finals of last year's FIFA Women's World Cup.
Along the way, Solo became only the second US women's team goalkeeper ever to reach 100 caps.
USADA Chief Executive Travis Tygart said in a statement: "As in all cases, we thoroughly investigate the circumstances and always do what is fair and right for clean athletes and the integrity of sport."