Donations of O-type blood have declined since mid-March and demand has increased, causing United Blood Services to ask the public for blood donations. They say the supply of O-negative and O-positive is extremely low. O-negative is a universal donor that can be transfused to anyone. O-positive is the most common blood type, and is in need all the time. Donations may be made at United Blood Services centers in Reno, Sparks, Carson City. Appointments can be made at bloodhero.com Walk-ins are also welcome.