UPDATE: On Thursday, April 2, the FDA eased restrictions on gay blood donors.

New York City resident Sabri Ben-Achour, 39, began to feel ill on March 12 and experienced roughly 36 hours of intense symptoms: fever, aches, fatigue, cough and headache.

But by March 14, Ben-Achour felt back to normal, except for one thing: Both his sense of smell and taste were gone.

"I couldn't smell anything," he said. "I could literally not smell s---." He ordered from an Indian restaurant: "I asked them to make it extra salty and extra spicy, and it tasted like water."

By March 16, he was fairly certain he had contracted and recuperated from COVID-19, the disease caused by the coronavirus. But like countless other New Yorkers who fell ill over the past six weeks, he heeded official advice not to take a test unless he was seriously ill.

Last week, however, he saw an advertisement for the Mount Sinai Health System's convalescent plasma study — an effort to collect the antibody-rich plasma of people who have recovered from COVID-19 and inject it into critically ill patients. He applied online right away.

After a Mount Sinai screener asked him a few intake questions about his prior symptoms and the medications he is taking, namely the HIV-prevention pill Truvada, Ben-Achour made an appointment to go to the hospital, where he had his blood drawn Saturday.

Full coverage of the coronavirus outbreak

On Monday, he got a phone call: He had, indeed, contracted and recovered from COVID-19, his blood had a "robust" level of antibodies, and the Mount Sinai doctors wanted him to donate his blood as quickly as possible so his plasma could be extracted and used in an experimental infusion on critically ill COVID-19 patients.

He was given an appointment Tuesday at the New York Blood Center and received a text with instructions to eat food and drink water before showing up. But just a few hours before his appointment, he said, he got a call from Mount Sinai saying, "Actually, you're not going to be able to donate because you are on Truvada."

Ben-Achour, who is gay and HIV-negative, daily takes a Truvada pill, also known as pre-exposure prophylaxis, or PrEP, to protect himself against HIV infection. PrEP users take an HIV test four times a year to verify that they are still HIV-negative, which is a prerequisite for a Truvada prescription.

Ben-Achour asked whether he could stop taking Truvada for a month and then donate his antibody-rich plasma, but he was told no: To donate any blood byproducts, he would have to both stop taking Truvada and — as is the policy for all men who have sex with men — abstain from sex for 12 months.

"I would be more than happy to go off of Truvada for four weeks," he said. "But obviously not for a year — that would be putting myself in danger."

The New York Blood Center, which declined to take his blood, said it was following federal and industry guidelines.

"We are accredited by AABB (formerly the American Association of Blood Banks) and we follow their protocols, as well as FDA guidelines," a spokesperson for the center told NBC News.

The restrictions date to 1983, during the height of the AIDS crisis, when the federal government instituted a lifetime ban on blood donations by any man who had ever had sex with another man. The rule, intended to keep HIV out of the blood supply, was replaced in 2015 with a regulation that requires a year of abstinence to donate blood.

Download the NBC News app for full coverage and alerts about the coronavirus outbreak

Restrictions on blood donations from gay and bisexual men — who represent about 70 percent of all new HIV infections in the U.S. — have come under increased scrutiny in recent months, particularly after coronavirus fears forced the cancellation of many in-person blood drives, causing an acute blood shortage amid a pandemic.

In November, the American Red Cross called for technological changes that could better address concerns about HIV in the blood supply and suggested that the required period of abstinence be shortened from 12 to three months, as is the policy in Canada and Britain.