Currently, the FDA bans gay and bisexual men (and any other man who has had sex with men [MSM]) from giving blood. If a man has had sex with another man even once since 1977, he is permanently disqualified from donating blood. The ban is a relic of the AIDS panic of the 80's, when HIV/AIDS was "the gay disease", couldn't be tested for reliably, etc. It made sense then. But now? Now, HIV affects every demographic. Now, it can be detected by testing within 2 weeks of exposure. And yet the rules are still such that if a man once had protected sex with another man 30 years ago, he will never be allowed to donate blood, while a man who has had sex with a known HIV-positive woman is only deferred for a year, after which he may donate blood again. This is anti-gay (and apparently is sometimes used as anti-trans, depending on the personnel at a given blood center) discrimination, pure and simple, and it needs to go away.
Right now, the FDA is convening a committee on whether or not to reconsider the ban. They are open to public comments. Please, email Dr. Holmberg - firstname.lastname@example.org - to encourage the committee to replace the ban with a policy grounded in science in fact, rather than discrimination. Additional talking points and a form letter can be found here, if you want to use that.