CHICAGO (WLS) -- Supplies of two universal blood types are low here in the Chicago area.
LifeSource is urging people with O-positive and O-negative blood to make a donation.
They say O-positive is the most common blood type, and most people can accept O-negative regardless of their blood type.
According to LifeSource, O-negative the type most commonly used in trauma cases.
Chicago area low on two universal blood types