Retinol-binding protein (RBP) is an unglycosylated protein synthesised by the liver. The role of RBP is to transport retinol (vitamin A) from the liver to the target tissues (retina, skin, etc.) in the bloodstream. This protein is then metabolised, filtered and reabsorbed in the kidney. RBP is a sensitive marker of undernutrition and the monitoring of its serum concentration allows the monitoring of nutritional status. Decreased RBP serum and plasma levels are also observed in the event of hypovitaminosis A, tubular nephropathies, hepatocellular insufficiency or severe or acute inflammation. An increase in RBP is correlated with of glomerular renal failure, type 2 diabetes or steatosis.