What this test measures
Serum zinc measures the circulating zinc pool (~0.1% of total body zinc) — the most accessible biomarker for deficiency screening. Zinc is a cofactor for over 300 enzymes including alkaline phosphatase, RNA polymerase, alcohol dehydrogenase and carbonic anhydrase; it is essential for cell-mediated immunity, growth, taste, smell, wound healing and male fertility.
Why it matters
Zinc deficiency affects an estimated 30–60% of Indian children, pregnant women, and the elderly per ICMR and INDIAB data — driven by cereal-dominant diets rich in phytates (which block absorption) and modest meat/seafood intake. Clinical features include impaired linear growth, frequent infections, delayed wound healing, peri-oral and acral dermatitis, alopecia, taste / smell disturbance and (in inherited acrodermatitis enteropathica) severe skin lesions. WHO recommends zinc as adjunct therapy in childhood diarrhoea, and Indian PHC programmes routinely stock zinc tablets.
How to prepare
Fast 8–12 hours, collect a morning sample, use a trace-metal-free royal-blue-top tube. Stop zinc supplements 24 hours before unless monitoring on therapy. Note any acute illness (acute-phase response lowers serum zinc transiently). Avoid haemolysis — red cells have ~10x serum zinc and can dramatically falsely elevate the reading.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Serum Zinc (µg/dL)[1] | 70 – 120 | < 60 — deficiency. Investigate intake (cereal-heavy diet), losses (chronic diarrhoea, burns), increased need (pregnancy, growth spurts), or malabsorption (coeliac, IBD, post-bariatric). Re-check alkaline phosphatase (often low in deficiency). Supplement 20–40 mg/day for adults; 10–20 mg/day for children; re-test in 3 months. | > 130 — usually over-supplementation (zinc lozenges, high-dose multivitamins) or pre-analytical haemolysis. Sustained high-dose zinc can induce copper deficiency. |
Serum zinc bands
| Zinc (µg/dL) | Status | Action |
|---|---|---|
| < 50 | Severe deficiency | Supplement 40–60 mg/day elemental, identify cause, re-test 3 months |
| 50 – 69 | Mild–moderate deficiency | Supplement 20–40 mg/day, dietary advice, re-test 3 months |
| 70 – 120 | Normal | No action |
| > 130 | High — usually supplements / haemolysis | Review intake; check serum copper if sustained |
Frequently asked questions
What's the difference between Serum Zinc and Plasma Zinc?
Functionally the same — both measure the small circulating zinc pool. Most Indian labs report "serum zinc". Use a trace-metal-free tube and a fasting morning sample for either.
Should I stop my zinc supplements before the test?
Yes, stop for 24 hours unless you specifically want to confirm therapeutic levels while on treatment.
Are vegetarian diets at higher risk of deficiency?
Yes. Vegetarian / vegan diets provide less bioavailable zinc — animal sources are easier to absorb. Indian vegetarian diets dominated by polished rice and wheat fall short; soaking, sprouting and fermentation (idli, dosa, dhokla) reduce phytates and improve absorption.
My alkaline phosphatase is low — could it be zinc?
Quite possibly. ALP is zinc-dependent, and low ALP in an otherwise well person should prompt a serum zinc check.
How quickly do levels recover?
4–8 weeks for mild deficiency on adequate supplementation; 3 months or more for severe cases or when the cause persists.
Related Toxicology / Trace Elements tests
Tests commonly ordered alongside SERUM ZINC, or that help interpret an unexpected result.
Sources & references
- NIH ODS — Zinc Fact Sheet for Health Professionals · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Zinc, Plasma/Serum · accessed 2026-05-30T00:00:00.000Z
- ICMR-NIN — Nutrient Requirements for Indians (2020) · accessed 2026-05-30T00:00:00.000Z
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