Zinc, RBC

The Zinc, RBC test (red blood cell zinc; Zn RBC; zinc, blood) is used to assess zinc balance and to aid in diagnosing zinc deficiency, including subclinical deficiency. It is also ordered when zinc intoxication is suspected or when there is concern for industrial or workplace exposure to zinc. Results are interpreted in conjunction with the clinical presentation and other laboratory data to contextualize potential physiologic and exposure-related influences on zinc measurements.

Zinc supports normal growth, cellular differentiation, and membrane integrity, and it functions as a cofactor for a broad array of enzymes and DNA-binding transcription factors (zinc-finger proteins). Dietary zinc is obtained from meat, dairy, seafood, grains, nuts, and vegetables. Absorption occurs primarily in the duodenum and jejunum, is facilitated by animal proteins, and is inhibited by phytates and iron. Both deficiency and excess zinc adversely affect multiple organ systems. Circulating zinc concentrations can decrease with acute infection or inflammation, trauma, strenuous exercise, stress, and after meals, so interpretation requires correlation with the clinical setting and other laboratory findings. Acute zinc intoxication can follow ingestion from galvanized containers, and chronic excess may impair copper absorption. Inhalation of metal oxide fumes that include zinc can trigger metal fume fever; blood zinc can be elevated in this context but is not specific for the condition.