For some people, a national tragedy was the catalyst to start giving. For others, it was a personal loss.
"My friend Joey, he needed blood," said Ashley Perry, a phlebotomist with the Red Cross. "He would go into the hospital and get donations at least once a month, if not more, and those donations really helped him, and without them, he probably wouldn't have lived as long as he actually did."
But donors like her are in critical demand. Across the country, donor stations are empty and hospitals and patients are in a precarious position.
"We haven't had to cancel surgeries yet -- we have in years past," said Cliff Numark, CEO, American Red Cross Blood Services Southern California. "But we never want to get to that stage where surgeries are postponed. So literally there are minute-by-minute decisions to determine which patients are served and which ones aren't."
Southern California always has a blood shortage and relies on other regions to provide 20 percent of the blood supply. But with severe weather in parts of the country and nationwide donations falling, that supply is cut short.
On top of that, about 20 percent of the blood supply comes from high school and college students, who are currently on summer break.
"You really do save someone," said Perry. "It sounds cheesy, but it's true."