Zinc is essential for immune function, protein synthesis, wound healing, DNA synthesis, and cell division. It also supports normal growth and development during pregnancy, childhood, and adolescence. Zinc deficiency can lead to growth retardation, hair loss, diarrhea, and delayed sexual maturation, while excess zinc can cause nausea, vomiting, and interfere with copper absorption. Testing zinc levels aids in diagnosing these conditions and ensuring proper zinc balance.