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Immunoassay for Retinol-Binding Protein (RBP) in Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures the level of retinol-binding protein (RBP) in your blood serum. RBP helps transport vitamin A, a vital nutrient for vision, immune function, and cell growth.

Quick summary

["RBP levels can indicate vitamin A status and potential deficiencies or liver function issues."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
33516-6
Short code
Imm Retics NFr
Synonyms
Imm Retics NFr
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What Is Retinol-Binding Protein (RBP)?

Retinol-binding protein (RBP) is a protein in your blood that carries vitamin A (retinol) to tissues where it’s needed. Low levels of RBP can signal vitamin A deficiency or liver problems, as the liver produces RBP to transport vitamin A.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms like night blindness, dry skin, frequent infections, or if you’re at risk for vitamin A deficiency (e.g., poor diet, malabsorption). It may also be used to monitor liver health or assess vitamin A status in certain conditions.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The sample is sent to a lab for an immunoassay test, which detects the presence and quantity of RBP in your serum.

What Do Results Mean?

Results are compared to a reference range for your age and health status. Low RBP levels may suggest vitamin A deficiency or liver dysfunction, while high levels could indicate dehydration or other conditions. Your doctor will interpret results in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

RBP Serum Test

Frequently asked questions

What causes low RBP levels?
Low RBP levels may result from vitamin A deficiency, liver disease (such as cirrhosis), chronic kidney disease, or conditions affecting protein synthesis in the body.
Can diet affect RBP test results?
Yes, your diet can influence RBP levels. A diet low in vitamin A or protein may lead to lower RBP. Your doctor may recommend dietary adjustments or supplements if deficiencies are suspected.
How often should this test be repeated?
The frequency depends on your health status. If you have a known condition like liver disease or vitamin A deficiency, your doctor may recommend periodic testing to monitor changes in RBP levels.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy