Zinc, Plasma or Serum

Zinc may be elevated with zinc supplementation or fasting. Elevated zinc concentrations may interfere with copper absorption.

Elevated results may be due to skin or collection-related contamination, including the use of a noncertified metal-free collection/transport tube. If contamination concerns exist due to elevated levels of serum/plasma zinc, confirmation with a second specimen collected in a certified metal-free tube is recommended.

Zinc depletion occurs either because it is not absorbed from the diet (excess copper or iron interfere with absorption) or it is lost after absorption. Dietary deficiency may be due to absence (parenteral nutrition) or because the zinc in the diet is bound to phytate (fiber) and not available for absorption. Excess copper and iron in the diet (eg, iron supplements) interfere with zinc uptake. Once absorbed, the most common route of loss is via exudates from open wounds or gastrointestinal loss. Zinc depletion occurs in burn patients who lose zinc in the exudates from their burn sites. Hepatic cirrhosis causes excess loss of zinc by enhancing kidney excretion. Other diseases that cause low serum zinc are ulcerative colitis, Crohn disease, regional enteritis, sprue, intestinal bypass, neoplastic disease, and increased catabolism induced by anabolic steroids. The conditions of anorexia and starvation also result in low zinc levels.

In healthy individuals, plasma or serum zinc are reliable markers of zinc status, mainly reflecting zinc intake. Because the effective regulation of zinc homeostasis buffers the functional response to dietary deficiency and excess, plasma zinc levels are generally considered a poor measure of marginal zinc deficiency.