Albumin is a protein that is characterized by its solubility in water, as distinct from globulin, which is insoluble or only partially soluble in water. Albumin is the major protein component of human serum. Albumin is the major contributor to colloidal osmotic pressure of plasma. In addition, it binds and transports many metallic ions, drugs, metabolites, and hormones.
In human serum normal levels of serum albumin are 3.2-5.7 gm/dl. Low levels of serum albumin are usually associated with altered body fluid distribution and edema. Increased levels can be associated with severe dehydration. Decreased levels may be associated with acute phase response (inflammation, infection, trauma, surgery, malignancy, etc.), nephrotic syndrome, malnutrition, pregnancy, liver disease, or genetic predispositions.
For a variety of reasons, serum albumin can also be found in urine, a condition known as albuminuria. For example, microalbuminuria (defined as the persistent elevation of urinary albumin above 20 μg/minute or 30 mg/24 hours) occurs long before clinical proteinuria becomes evident, and can be associated with increased risk of renal failure. Monitoring is often helpful in managing early stage diabetes.