Adult preferred minimum: 1 mL serum or plasma Adult absolute minimum: 0.3 mL serum or plasma Pediatric Minimum: 0.2 mL serum or plasma

0-1 month 0.18 - 0.50 mg/L 2 months-12 years 0.20 - 0.50 mg/L 13-17 years 0.26 - 0.70 mg/L 18+ years 0.30 - 1.2 mg/L Retinyl Palmitate 0 - 0.10 mg/L

Draw sample following an overnight (12 hour fast). Patient should not consume alcohol for one day prior to blood draw. Analysis includes Retinol and Retinyl Palmitate. This assay does not measure other Vitamin A metabolites such as retinaldehyde and retinoic acid. Serum retinol is typically maintained until hepatic stores are almost depleted. Values > 0.30 mg/L probably represent adequate liver stores, whereas values < 0.10 mg/L indicate deficiency. Vitamin A toxicity occurs when retinol exceeds the capacity of retinol binding protein (RBP). Individuals with compromised renal function can retain RBP and may, therefore, have moderate retinol elevations. Drugs which interfere with Vitamin A analysis include probucol (Lorelco).