Zinc
Zn· also: Zinc, Serum Zinc
Clinical Overview
Zinc is an essential trace mineral that serves as a structural component of hundreds of enzymes and transcription factors involved in immune function, wound healing, DNA synthesis, cell division, and sensory function (taste and smell). The body has no zinc storage system — a regular dietary supply is essential. Zinc deficiency is the fifth leading nutritional risk factor for disease globally.
Why This Test Matters
Zinc deficiency impairs immune function (T cell–mediated immunity), wound healing, and growth in children. It is a significant cause of morbidity in developing countries, contributing to diarrhea, pneumonia, and growth faltering. Measurement of serum zinc is challenging because it is an acute-phase reactant (falls during inflammation) and has a wide normal range. Clinical evaluation (dietary history, symptoms) alongside serum zinc is needed for diagnosis. Supplementation of zinc for the common cold has evidence for reducing duration when started within 24 hours of symptom onset.
Reference RangesWHO/IFCC standards
| Age Group | Reference Range | Unit | Notes |
|---|---|---|---|
| Adults (18–64) | 70 – 120 | µg/dL | — |
Also reported in: µmol/L.
What Causes Abnormal Results?
High Zn Causes
- Zinc supplementation (excessive doses)
- Industrial exposure (zinc fume fever)
- Zinc-containing denture creams (chronic copper deficiency from zinc excess is the main risk)
Low Zn Causes
- Inadequate dietary intake (common in vegetarians, vegans, elderly)
- Malabsorption (Crohn's disease, celiac disease, short bowel syndrome)
- Alcoholism (increased urinary zinc excretion)
- Acrodermatitis enteropathica (rare genetic zinc malabsorption disorder)
- Burns and major trauma (increased losses)
- Chronic kidney disease
- Sickle cell disease
- Total parenteral nutrition without zinc supplementation
Signs & Symptoms to Watch For
How to Prepare for This Test
Draw in the morning fasting. Use trace element–free tubes (royal blue-top, zinc-free). Avoid contamination from rubber stoppers or metal needles, which can falsely elevate zinc.
Factors That Can Affect Results
- Acute phase reaction (zinc is a negative acute phase reactant — infection and inflammation lower serum zinc without true deficiency)
- Meals (postprandial zinc levels fluctuate)
- Hemolysis (zinc intracellular — hemolysis raises serum zinc)
- Contamination from sample collection equipment
- Oral contraceptives and estrogen (lower serum zinc)
Related Topics
Frequently Asked Questions
Does zinc supplementation help with COVID-19 or respiratory infections?
Zinc plays a role in immune function and antiviral defense. Evidence for zinc in preventing or treating COVID-19 is inconclusive. For the common cold (rhinovirus), meta-analyses suggest zinc lozenges or syrup started within 24 hours of symptom onset reduce duration by approximately 1–2 days. Zinc supplementation is most clearly beneficial in people who are actually deficient. Routine high-dose supplementation in zinc-sufficient individuals has not been proven beneficial and can cause copper deficiency at doses above 40 mg/day long-term.
Can excess zinc cause harm?
Yes. Chronic high-dose zinc intake (>150 mg/day) can cause copper deficiency by competing for intestinal absorption (both use the same transporter, ZIP4). Copper deficiency causes anemia, neutropenia, and neurological problems mimicking B12 deficiency (myelopathy). This complication has been reported in people using excessive zinc supplements or zinc-containing denture adhesive creams. The tolerable upper intake level for zinc is 40 mg/day for adults.