The Food and Drug Administration announced on Thursday that it was significantly loosening its recommendations for blood donations from gay and bisexual men, reducing the amount of time men who have had sex with men should wait before they give blood to three months from one year in hopes of ameliorating a drastic drop in supply during the coronavirus pandemic.

The earlier 12-month waiting period was intensely criticized as discriminatory and antiquated when the F.D.A. introduced it in 2015 to replace a lifetime prohibition on blood donation by gay and bisexual men.

That ban was enacted in 1983, early in the AIDS epidemic when little was known about the human immunodeficiency virus that caused the disease. The F.D.A. re-examined the ban over the years, but had maintained that the restriction was necessary to keep the blood supply safe and untainted by H.I.V.

In support of its change on Thursday, the agency said in a statement that based on recent studies, it had “concluded that current policies regarding certain donor eligibility criteria can be modified without compromising the safety of the blood supply.”