The U.S. is running low on blood. Here's why that's dangerous

The U.S. blood supply has reached crisis levels, prompting the American Red Cross and the Surgeon General's Office to urge people to donate. Why it matters: A prolonged blood shortage could delay surgeries, trauma care and other treatments that depend on timely blood transfusions. The Red Cross says it has "less than a one-day national supply of type O positive blood," which is the most commonly transfused blood type. Due to the shortage, the organization is limiting distribution of type O…