Under normal physiological conditions, significant amounts of hemoglobin are not found in plasma. Hemoglobin is primarily contained within red blood cells (erythrocytes).
While small amounts of "free hemoglobin" (hemoglobin outside of red blood cells, also referred to as plasma hemoglobin) may be present, it is typically rapidly cleared by the body's mechanisms. Elevated levels of free hemoglobin in the plasma can indicate hemolysis (the breakdown of red blood cells).
