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MIAMI (CBSMiami) – Every two seconds, someone in the United States needs a blood transfusion.

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Now a major blood shortage has the American Red Cross issuing an emergency call for donations.

Lori Lawrence knows how critical it is to give blood, that’s why she makes sure to donate every two months.

One of my daughters had a number of surgical procedures when she was little, and she needed blood at the time,” said Lawrence. “I know its very necessary.”

The Red Cross is hoping more people get the message and roll up their sleeves. They say the nation is facing a shortage because of all the snowy, cold weather across much of the country.

“As you would expect, we have to cancel blood drives because of inclement weather, but this year we have canceled 300 blood drives since December 1st,” said American Red Cross CEO Gail McGovern.

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Donations also typically fall off over the holidays. The agency said centers are now struggling to keep up with demand, blood and platelets are being sent to hospitals faster thatn donations are coming in.

The Red Cross plans to extend hours at many of its sites over the next few weeks, to try to bring in more donors.

Jenna Lindsley, 21, said when she heard about the emergency, she went and donated immediately.

“There is no reason not to come. Its just takes an hour out of my day,” said Lindsley. “There is no reason not to give.”

Lindlsey adds that it’s the right thing to do and it can save lives.

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The Red Cross is responsible for about 40 percent of the nations blood supply.