O negative is a blood type characterized by the absence of A and B antigens on the surface of red blood cells, as well as the absence of the Rh factor. This makes it a universal donor type, meaning individuals with O negative blood can donate to anyone, regardless of their blood type. People with O negative blood make up about 7% of the population. Due to its universal compatibility, it is often in high demand for blood transfusions and emergency situations, making it crucial for blood banks and hospitals to maintain an adequate supply of this type.