"People perceive of giving blood as a civic duty," Moulton added. "The current policy puts gay and bisexual men who are going to be honest in an awkward position during a blood drive. People ask, 'Why aren't you giving blood?'"
The FDA acknowledges that the ban leads to rejection of many healthy donors.
However, it says the policy "minimizes even the small risk of getting infectious diseases such as HIV or hepatitis through a blood transfusion." And it says the blood supply in the U.S. has been stable.
Susan Stramer, executive scientific officer with the American Red Cross, agrees that the magnitude of the blood supply isn't a decisive factor in the debate.
"We have a surplus of blood," she said. "The question is about what's equitable."
The push for changing the policy gained momentum in 2006, when the Red Cross, the American Association of Blood Banks, and America's Blood Centers reported to an FDA-sponsored workshop that the ban "is medically and scientifically unwarranted."
Over the next few years, the California State Assembly and the city councils in New York and Washington, D.C., urged repeal of the ban.
Faced with such appeals, HHS sought input in 2010 from its Advisory Committee for Blood Safety and Availability. The committee concluded that the donor-screening policy is "suboptimal" — permitting some potentially high risk donations while preventing some low risk donations — but recommended that the ban on donations by gay and bisexual men be retained pending further research.
In March 2012, HHS asked for comments on a possible pilot study to assess alternatives that would permit some gay and bisexual men to donate blood while maintaining the current high level of blood safety. That study has yet to begin.
Regardless of the pilot study's fate, Stramer said it's possible federal officials could gather enough data from other ongoing research to make an incremental change, such as emulating Canada by barring donors who've had male-on-male sex during the previous five years.