Blood has the characteristics of both a colloid and a suspension and is therefore a colloidal suspension. Since blood has characteristics of all three mediums, its true nature is hard to ascertain.
Blood in its normal, stable state is a suspension, which is a colloid. When acted upon by an external force, such as a centrifuge, blood separates into its separate components just as a suspension does.
A suspension, according to Chemicool, is a substance with particles that are large enough to settle. This process occurs in blood when it is outside the body. Settling does not occur within the body due to blood's colloidal characteristics.