Blood protein for transfusions. Bottle containing human serum albumin (HSA), a protein made by the liver and found in plasma, the liquid component of blood. HSA is important for transporting hormones, fatty acids and drugs around the blood. It also maintains blood pH and the concentrations of molecules in the blood (plasma volume). HSA solution is used to treat patients with liver diseases, such as cirrhosis, and hypoalbuminaemia (abnormally low blood albumin levels). This 4.5% HSA solution is equal in concentration to that in healthy blood plasma and is used in treating chronic disorders. Severe acute cases of low plasma volume (hypovolemic shock) are usually treated with a more concentrated 20% solution.