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Zinc (Zn)

SI UNITS (recommended)

CONVENTIONAL UNITS

(Essential Trace Element - Required for Enzymes, Immunity, Growth, Skin Health & Reproduction)

Synonyms

  • Zn
  • Serum zinc
  • Plasma zinc
  • Trace element zinc
  • Zinc ion (Zn²⁺)

Units of Measurement

  • µmol/L
  • µg/mL
  • µg/dL
  • µg/100 mL
  • µg%
  • µg/L
  • mg/L

Unit Conversions

Atomic Weight of Zinc = 65.38 g/mol

µmol/L ↔ µg/L

1 µmol/L=65.38 µg/L1\ \text{µmol/L} = 65.38\ \text{µg/L}1 µmol/L=65.38 µg/L 1 µg/L=0.0153 µmol/L1\ \text{µg/L} = 0.0153\ \text{µmol/L}1 µg/L=0.0153 µmol/L

µg/mL → µg/L

1 µg/mL=1000 µg/L1\ \text{µg/mL} = 1000\ \text{µg/L}1 µg/mL=1000 µg/L

µg/dL → µg/L

1 µg/dL=10 µg/L1\ \text{µg/dL} = 10\ \text{µg/L}1 µg/dL=10 µg/L

mg/L ↔ µmol/L

1 mg/L=1000 µg/L=15.3 µmol/L1\ \text{mg/L} = 1000\ \text{µg/L} = 15.3\ \text{µmol/L}1 mg/L=1000 µg/L=15.3 µmol/L

µg/100 mL = µg% = µg/dL

Description

Zinc is an essential trace element involved in over 300 enzymes, critical for:

  • Immune function
  • Growth and development
  • Protein and DNA synthesis
  • Wound healing
  • Skin integrity
  • Taste and smell
  • Reproductive function
  • Antioxidant defense (via Zn–Cu superoxide dismutase)

Zinc is mainly stored in:

  • Muscle (60%)
  • Bone (30%)
  • Skin and liver

Only 0.1% of total body zinc is in plasma, making levels sensitive to inflammation, stress, and meals.

Physiological Role

1. Enzymatic Cofactor

Involved in:

  • RNA/DNA polymerases
  • Carbonic anhydrase
  • Alcohol dehydrogenase
  • Alkaline phosphatase
  • SOD antioxidant enzyme

2. Immune Function

Deficiency reduces:

  • T-cell number
  • NK cell activity
  • Antibody response

3. Growth & Development

Required for:

  • Fetal growth
  • Childhood development
  • Pubertal maturation

4. Skin & Wound Healing

Maintains epithelial barrier integrity.
Deficiency causes:

  • Dermatitis
  • Alopecia
  • Poor healing

5. Reproduction

Low zinc affects:

  • Spermatogenesis
  • Gonadal function

Clinical Significance

LOW ZINC (Hypozincemia)

Most clinically important.

Causes

  • Poor intake (elderly, low-protein diet)
  • Malabsorption:
    • Celiac disease
    • Crohn’s
    • Short-bowel syndrome
    • Chronic diarrhea
  • Liver disease
  • Chronic alcoholism
  • Chronic kidney disease
  • High phytate diet (binds zinc)
  • Pregnancy / lactation
  • Burns / critical illness
  • Acrodermatitis enteropathica (ZIP4 gene defect)

Symptoms

  • Dermatitis (periorificial, acral)
  • Alopecia
  • Loss of taste/smell
  • Diarrhea
  • Delayed wound healing
  • Poor appetite
  • Growth retardation (children)
  • Hypogonadism (men)
  • Night blindness
  • Frequent infections

HIGH ZINC (Hyperzincemia)

Usually from supplements or contaminated tubes.

Causes

  • Excess supplementation
  • Denture creams
  • Hemolysis or contamination from zinc-coated needles
  • Industrial exposure

Symptoms

  • Nausea, vomiting
  • Abdominal pain
  • Immune suppression
  • Low copper → anemia, neutropenia
  • Metallic taste

Reference Intervals

(Tietz 8E • Mayo Clinic • ARUP • WHO)

Serum Zinc

  • 10 – 18 µmol/L
     (= 650 – 1180 µg/L)
    (= 65 – 118 µg/dL)
    (= 0.65 – 1.18 µg/mL)
    (= 0.65 – 1.18 mg/L)

Deficiency

  • <10 µmol/L (<650 µg/L)

Critical deficiency

  • <5 µmol/L (<325 µg/L)

Plasma zinc decreases in acute illness, inflammation, pregnancy, even when total body zinc is normal.

Diagnostic Uses

1. Evaluation of Malnutrition / Malabsorption

Common in GI disorders.

2. Growth Delay in Children

Nutritional zinc assessment.

3. Chronic Diarrhea

Major cause of zinc loss.

4. Immune Dysfunction / Frequent Infections

5. Skin Disorders

  • Dermatitis
  • Poor wound healing

6. Liver Disease Workup

Cirrhosis commonly causes zinc deficiency.

7. Acrodermatitis Enteropathica

Genetic zinc malabsorption.

8. Critical Care / Sepsis

Zinc drops dramatically during inflammation.

Analytical Notes

  • Use trace element–free (royal blue-top) tubes.
  • Hemolysis falsely elevates zinc (RBCs contain zinc).
  • Morning fasting sample preferred (post-meal ↓ levels).
  • Avoid contamination from:
    • Needles
    • Rubber stoppers
    • Metal instruments
  • Measured via ICP-MS or AAS.

Clinical Pearls

  • Zinc supplementation can cause copper deficiency (competes for absorption).
  • Zn deficiency + skin lesions + diarrhea in infants → think acrodermatitis enteropathica.
  • Vegetarian diets may reduce zinc bioavailability (phytates bind zinc).
  • In acute inflammation, serum zinc drops, but deficiency is not always true.
  • Alcohol use disorder is a major cause of chronic zinc deficiency.

Interesting Fact

Zinc is the second most abundant trace metal in the human body after iron, and it is essential for the structural integrity of zinc-finger proteins involved in gene regulation.

References

  1. Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Trace Elements
  2. WHO Micronutrient Guidelines - Zinc
  3. NIH Office of Dietary Supplements - Zinc
  4. Mayo Clinic Laboratories - Zinc Test
  5. ARUP Consult - Trace Element Interpretation
  6. MedlinePlus - Zinc Testing

Last updated: January 27, 2026

Reviewed by : Medical Review Board

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