What is the Retinol Binding Protein test?

The Retinol Binding Protein (RBP) blood test measures the level of a transport protein responsible for carrying vitamin A (retinol) from the liver to peripheral tissues. RBP binds retinol in circulation, allowing vitamin A to be delivered to organs such as the eyes, immune system, and skin.

RBP is produced by the liver and cleared by the kidneys. Because of this dual role, RBP levels can reflect vitamin A status, liver function, and kidney tubular function. Changes in RBP may occur before changes in serum vitamin A levels.

This test is often used in nutritional assessment and in the evaluation of kidney-related protein loss.

Why do I need a test for Retinol Binding Protein?

Abnormal RBP levels may indicate vitamin A deficiency, impaired liver synthesis, or kidney tubular dysfunction. Measuring RBP provides insight into both nutritional status and renal protein handling.

It is particularly useful when vitamin A deficiency is suspected or when kidney function abnormalities are being investigated.

You may benefit from this test if you experience or have:

• Suspected vitamin A deficiency

• Poor night vision or eye dryness

• Frequent infections or impaired immunity

• Malnutrition or malabsorption disorders

• Chronic liver disease

• Kidney disease or tubular dysfunction

• Protein loss in urine

• Monitoring nutritional status in chronic illness

Benefits of the Retinol Binding Protein test

1. Assesses vitamin A transport
   Reflects availability of retinol to tissues.

2. Detects early nutritional deficiency
   Changes may occur before serum retinol drops.

3. Supports kidney tubular function assessment
   Elevated urinary loss or low blood levels suggest tubular damage.

4. Assists liver function evaluation
   RBP synthesis depends on liver health.

5. Useful in malnutrition assessment
   Sensitive marker of protein-energy malnutrition.

6. Supports immune and visual health investigation
   Vitamin A is essential for both systems.

7. Complements vitamin A testing
   Adds functional insight beyond retinol levels alone.

8. Non-invasive nutritional and renal marker
   Requires only a blood sample.

Step-by-step – how we offer Retinol Binding Protein testing

Clinic-based testing (UK-wide)

• Choose your nearest UK clinic

• Attend your appointment

• Blood sample collected by a qualified clinician or phlebotomist

• Sample is sent to the laboratory for analysis

At-home or hotel testing (+£60)

• A qualified phlebotomist visits your home or hotel

• Blood sample collected in a comfortable, familiar setting

• No clinic visit or travel required

Both services are available UK-wide.

Your Retinol Binding Protein results explained

Low RBP levels

Low RBP levels may indicate vitamin A deficiency, malnutrition, liver disease, or increased loss due to kidney tubular dysfunction. Low levels can impair immune function and vision.

Clinical context and additional nutritional markers are important for interpretation.

UK reference interpretation:

• Low: Below laboratory reference range

Normal RBP levels

Normal levels suggest adequate vitamin A transport, normal liver synthesis, and appropriate kidney handling of the protein.

This indicates balanced nutritional and metabolic status.

UK reference interpretation:

• Normal: Within laboratory reference range

High RBP levels

Elevated RBP levels may be seen in reduced kidney clearance, insulin resistance, or metabolic disorders. High levels can reflect altered protein handling rather than excess vitamin A.

Further evaluation may be required.

UK reference interpretation:

• High: Above laboratory reference range