A blitz of publicity accompanied Yale’s American Red Cross blood drive last week, but many students who showed up at Payne-Whitney Gymnasium found that their blood was not wanted.

Numerous reasons prevent people from donating blood — from medications to tattoos to travel. The restrictions can be particularly limiting at a school like Yale, where students’ unique lifestyles and experience can disqualify them in large numbers.

By far the most common reason Elis are unable to donate, especially among women, is a low hematocrit — a measure of the percentage of red blood cells in the blood — which correlates with the amount of oxygen that can be carried. A normal hematocrit for women is 36 to 46 percent, while for men it is 40 to 50 percent. But since the blood is used in trauma and surgery situations where high oxygen capacity is imperative, the Red Cross requires a hematocrit of 38 percent in order to donate.

Wen Fan ’08, president of American Red Cross at Yale, said that many girls come in with hematocrits of 36 or 37.

“We tell them to go eat a lot of iron supplements and come back in a couple of days,” Fan said, adding, “Grape-nuts have 90% of the daily value of iron in half a cup.”

Jess Catlin ’10 did just that leading up to the blood drive. Now a member of the Yale’s American Red Cross chapter, she said that in high school she had been disappointed because she could not donate. This time, though, she was determined to contribute as more than an organizational volunteer.

“I made the effort to eat lots of things with iron in them for the week before to get up my hematocrit,” Catlin said. “I’m not a vegetarian, but I made an effort to eat extra red meat.”

Matt Skarzynski, who has taken blood for six years with the Red Cross, agreed that low hematocrits were mostly to blame for failed attempts to give blood last week. He said he thinks Yale’s health conscious environment contributed to students’ low iron levels.

“A lot of girls end up being vegetarian … and it’s hard to keep your iron up when you don’t eat the flesh of other animals,” Skarzynski said.

Students at Wesleyan University, which he said has a higher incidence of vegetarianism, had even lower hematocrits than Elis.

Where Yale really took the cake was in travel, he said, which accounted for the second largest group of people unable to donate.

Unsurprisingly, Skarzynski said, Yale students not only travel a lot outside of the country, but they tend to go to remote places.

“We’re looking stuff up in the atlas we’ve never even heard of,” he said.

Regulations based on travel can be incredibly complicated, as they vary not only by country but also by city or region. The primary restrictions prevent people from donating if they have lived for at least five years in Europe or in England for at least three months since 1980. The requirement relates to the possibility that someone may have contracted variant Creutzfeld Jacob Disease, the human form of what is commonly known as mad cow disease, by eating tainted meat.

The Red Cross explains that since there is evidence that vCJD can be transmitted through transfusions and there is no test to screen for it, special precautions are necessary to prevent infection.

The disease is thought to be caused by misfolded proteins, called prions, which propagate and slowly destroy the brain. According to a recent study by Yale School of Medicine professor Laura Manuelidis, a virus may actually be responsible for vCJD. If her claim is verified, the ban on blood donations from European residents and travelers would still remain in place.

International students are especially affected by the travel-based restrictions. Because of a rare form of HIV called Type O, which cannot always be detected through HIV tests, the Red Cross does not allow blood donations from anyone who was born or has lived in a wide area of Western Africa since 1977.

For the majority of Yale students, a more pressing issue is restrictions aimed at malaria. There is a temporary 12-month ban on donating after any visit to certain countries harboring malaria, and a three-year ban after a stay of five years or more.

But Fan said the rules aren’t as simple as they might seem, as evidenced by her impending trip to China. She plans on visiting Bejing and Shanghai — which are both free of malaria — but the method of transportation she uses to get from one to the other will affect whether or not she can donate. If she were to fly, she said, she would be in the clear, but a train or car, which do not provide a “closed environment,” would prevent her from giving blood for a year.

Various medications also require a waiting period before donations are allowed, often because the underlying condition would put the recipient at risk.

One prominent class of drugs that prevent donations is blood thinners, since blood will not clot normally. But the most commonly used blood thinner among college students — aspirin — only requires a 48-hour waiting period after the last dose.

Restrictions cause 12 percent of prospective donors to be deferred, said Donna Morrissey, a spokeswoman for the Northeast Division of American Red Cross Blood Services. Some of the restrictions, though, are more controversial than others.

Skarzynski said political objection to the ban on male donors who have had sex with other men sometimes lowers turnout at blood drives, especially on college campuses. The rule was instituted following highly publicized incidents of patients contracting HIV from transfusions in the earlier years of the HIV/AIDS epidemic.

While the ban rarely becomes a public issue at Yale, Skarzynski said, silent protests are common at Wesleyan. He said it is possible that there could be a change in policy over the next few years in which men would have to wait 12 months, or some other temporary period, after having sex with other men before giving blood.

Michaela Almeida, a spokeswoman for the Connecticut Region of the American Red Cross Blood Services, said the policy was not created by the Red Cross but rather mandated by the Food and Drug Administration. The rules apply equally to all blood banks, she said, though she said that the Red Cross has encouraged the FDA to reconsider its policies.

A gay senior who asked to remain anonymous said that while he cannot donate with the Red Cross because of the rule, he has given blood at a private blood center that did not ask any questions regarding male-male sexual contact. A representative at the private center, however, said it follows FDA regulations on the matter.

Despite the detailed list of restrictions, 60 percent of people nationally are still eligible to donate, she said, though only 5 percent choose to do so.

“That’s the main reason we rely on effective recruiting to get blood,” Almeida said. “We encourage people to call our hotline to find out who is eligible and who’s not.”