Following a difficult Fourth of July week for blood and platelet donations and ongoing challenges finding new blood donors, the American Red Cross announced Tuesday that it faces a blood shortage and has issued an emergency call for eligible individuals of all blood types to give now and prevent delays in medical care.

About 450 fewer blood drives were organized by businesses and other community groups last week than during a typical week as people across the country celebrated the holiday with activities and travel, ARC said.

This led to about 17,000 fewer blood donations than needed for patients in a single week, causing the Red Cross to now have less than a three-day supply of most blood types available—and less than a two-day supply of type O blood—for patients. At least a five-day supply is desired.

 “Medical emergencies and critical treatments don’t stop for holiday celebrations. Patients depend on lifesaving blood transfusions every day,” sa...