 Blood banks are facing a severe blood shortage and are urging everyone to roll up their sleeves to donate. The nonprofit blood bank Vitalant is facing an emergency shortage of type O blood, dropping to an 18-month low. O negative blood is the most in-demand type because it can be given to patients of any blood type, while O positive supports anyone with a positive blood type. Approximately 46% of the population has type O blood, which is crucial for overcoming this shortage.