American Red Cross declares second-ever national blood supply crisis

Donations to top US provider have dropped to four-year summer low with less than a day's supply of type O positive

The American Red Cross has declared the second-ever national blood supply crisis after blood donations fell to a four-year summer low.

On Monday, the 145-year-old non-profit said that as the United States' largest single provider of blood products, it now has less than one-day national supply of type O positive blood - the most commonly transfused blood.