How do I check my vitamin A levels?

From the Guidelines

To check your vitamin A levels, you should ask your healthcare provider to order a serum retinol blood test, which is the standard method for assessing vitamin A status, as recommended by the espen-espghan-ecfs guidelines on nutrition care for infants, children, and adults with cystic fibrosis 1. This simple blood test measures the amount of vitamin A in your bloodstream. Your doctor will likely recommend fasting for about 12 hours before the test for the most accurate results.

• Normal vitamin A levels typically range from 20-60 micrograms per deciliter (μg/dL), though reference ranges may vary slightly between laboratories.
• If you're experiencing symptoms like night blindness, dry eyes, skin problems, or frequent infections, these could indicate vitamin A deficiency and make testing more urgent.
• Your doctor might also check your levels if you have conditions that affect nutrient absorption like Crohn's disease or celiac disease. While vitamin A testing isn't part of routine bloodwork, it's particularly important if you're at risk for deficiency or toxicity, and monitoring is recommended annually, 3-6 months after a dosage change, and when pregnancy is considered, according to the guidelines 1. The test helps your healthcare provider determine if you need dietary changes or supplements to maintain optimal vitamin A levels for proper immune function, vision, and cell growth.

From the Research

Methods for Checking Vitamin A Levels

To check vitamin A levels, several methods can be employed, including:

• Blood tests to measure serum retinol and retinol-binding protein (RBP) levels 2, 3, 4
• Relative dose response test, which involves administering a dose of retinyl palmitate and measuring the response in serum retinol levels 3
• Analysis of liver autopsy or biopsy samples to directly measure vitamin A stores 2
• Isotope-dilution approach and pseudoequilibrium approach, which are still under development 2

Importance of Fasting Conditions

Fasting conditions are necessary for the accurate assessment of vitamin A status, especially in elderly adults, if spectrophotometric methods are used for measuring vitamin A 5

Biochemical Indicators of Vitamin A Deficiency

Two biochemical indicators are currently recommended for determining whether vitamin A deficiency is a public health problem:

• Serum retinol concentration, with a proposed cut-off of <0.70 micro mol/L (20 micro g/dL) in ≥15% of the sampled population 4
• Serum retinol-binding protein (RBP) concentration, although a reliable cut-off cannot be specified due to limited data 4

Measurement Techniques

Various measurement techniques can be used to assess serum retinol and RBP levels, including:

• High-performance liquid chromatography (HPLC) for serum retinol measurement 4
• Radial immunodiffusion (RID) for serum RBP measurement 4
• Fluorometric determination of retinol in serum, which is a rapid and relatively simple method 6