: Retinol-Binding Protein, Serum or Plasma, Mass Concentration

: What Is Retinol-Binding Protein?

: Retinol-binding protein is a small protein produced primarily by the liver. It binds to vitamin A (retinol) and transports it in the blood to tissues such as the eyes, skin, and immune system. Because the liver makes RBP, its level can offer clues about how well the liver is functioning and whether the body has adequate protein and vitamin A.

: Why Might This Test Be Ordered?

: Your healthcare provider may order an RBP test to help assess nutritional status, suspected vitamin A deficiency, or liver function. It can also be used when malnutrition or protein-energy deficiency is a concern, since RBP is sensitive to changes in protein intake and liver health.

: How the Sample Is Collected

: The test is performed on a blood sample, usually drawn from a vein in your arm. In most cases no special preparation is required, though your provider may give specific instructions. The sample is then analyzed in the laboratory to measure the concentration of RBP.

: What the Results Can Mean

: Results are interpreted alongside your symptoms, diet history, and other tests such as vitamin A, liver enzymes, and nutritional markers. Low RBP can occur with poor nutrition, liver disease, or certain inflammatory conditions, while results may also be affected by kidney function. Your provider will explain what your specific value means in context.