Information about a laboratory test
A high result can occur with supplementation, high exposure or conditions that alter handling of the nutrient; it does not automatically mean toxicity.
The Vitamin A (Retinol) test measures vision, immune function, epithelial tissues and vitamin A status.
Ordered when inadequate intake or absorption is suspected, in risk groups, or to assess supplement use; it is interpreted with related laboratory tests.
A low result can occur with inadequate intake, malabsorption, increased requirements or other clinical contexts; it does not identify the cause by itself.
A high result can occur with supplementation, high exposure or conditions that alter handling of the nutrient; it does not automatically mean toxicity.
Start with the performing laboratory's reference interval, unit, specimen type and method. Numeric information on this page is stored as sourced example intervals or clinical thresholds.
<= 20 mcg/dL
Retinol threshold associated with moderate vitamin A deficiency
This is a sourced clinical-context threshold and should not be used alone as a diagnosis or treatment decision. The laboratory report and clinical context take priority.
<= 10 mcg/dL
Retinol threshold associated with severe vitamin A deficiency
This is a sourced clinical-context threshold and should not be used alone as a diagnosis or treatment decision. The laboratory report and clinical context take priority.
Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.
Interpretation should consider method, supplements, diet, kidney/liver function and related biomarkers.
Vitamin A and Carotenoids – Health Professional Fact Sheet — NIH Office of Dietary Supplements
U.S. government nutrition reference · 2025 · Serum/plasma retinol and deficiency thresholds · Verified: Aug 12, 2026
Zinc – Health Professional Fact Sheet — NIH Office of Dietary Supplements
U.S. government nutrition reference · 2026 · Serum/plasma zinc status, typical concentrations and sex-specific inadequate-status cutoffs · Verified: Aug 12, 2026
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