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Blood Test Guide

Zinc Blood Test (Serum Zinc)

Zinc is essential for immunity, wound healing, taste, smell and hundreds of enzyme reactions. A serum zinc test measures your body's zinc status. Here's what the results mean.

Written and clinically reviewed by Suman Konda, PharmD, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last reviewed and updated: · How we check our content

Serum zinc reference ranges

GroupNormal RangeNotes
Adults (fasting AM sample)70–120 mcg/dL (10.7–18.4 µmol/L)Levels are highest in the morning before eating
Mild deficiency60–70 mcg/dLSubtle symptoms: fatigue, reduced immunity
Moderate deficiency40–60 mcg/dLHair loss, skin problems, poor wound healing
Severe deficiency<40 mcg/dLGrowth retardation, hypogonadism, acrodermatitis

Why zinc levels are tricky to measure

Important caveats for serum zinc

Serum zinc only captures about 0.1% of total body zinc: most zinc is inside cells. Serum levels fall during infections, inflammation and stress even when body stores are adequate (zinc is redistributed). For this reason, a normal serum zinc does not absolutely rule out deficiency, and levels should always be interpreted alongside symptoms and risk factors. Levels are highest in the morning before eating, so samples should be collected fasting in the morning for best accuracy.

What to Do When Inflammation Is in the Way

Plasma zinc is the standard measure of zinc status, and it is genuinely useful at the level of populations. Its weakness in an individual is that inflammation pushes it down independently of how much zinc you have.2 A sample taken during an infection, a flare of an inflammatory condition, or soon after surgery can read low in someone whose stores are perfectly adequate.

That has a consequence people rarely hear, and it concerns treatment rather than diagnosis. In a trial giving a micronutrient supplement containing zinc, plasma zinc rose by roughly 10% in participants without inflammation — and did not rise in those with it. Inflammation appeared to block the increase altogether.2 So a repeat level that has not moved after supplementation does not necessarily mean the supplement failed or that the dose was too low; it may mean the measurement is still being suppressed.

Two things that make the result interpretableA CRP taken at the same time, so a low zinc can be read in context rather than at face value. And, where the question is not urgent, a sample taken when you are well rather than during an illness. Timing also matters in a smaller way: zinc varies through the day and falls after eating, so a morning fasting sample is more comparable to the range.

It is worth saying that the effect of inflammation is not uniform across nutrients or situations. In a study of young children where more than half had a raised acute-phase protein, malaria infection clearly distorted ferritin and vitamin A markers — but plasma zinc was essentially identical in those with and without it.3 Zinc is affected by inflammation, but not by every inflammatory state to the same degree, which is a further reason to interpret one reading cautiously rather than to discard the test.

The practical position: a low plasma zinc in someone with risk factors and matching symptoms is worth acting on. A low plasma zinc taken during an acute illness, in someone without either, is worth repeating before concluding anything.

Symptoms of zinc deficiency

SymptomWhy it happens
Hair loss (telogen effluvium)Zinc is required for hair follicle function and cell division
Poor wound healingZinc activates collagen synthesis enzymes
Loss of taste and smell (ageusia/anosmia)Zinc-dependent enzymes in taste buds and olfactory neurons
Frequent infectionsZinc is essential for T-cell immune function
White spots on nails (leukonychia)Classically associated with zinc deficiency
Acne and slow-healing skinZinc regulates oil glands and has anti-inflammatory properties
Reduced fertility (men)Zinc is concentrated in sperm and needed for testosterone production

Who is at risk of zinc deficiency?

High-risk groups

Vegetarians and vegans (plant zinc is less bioavailable than meat zinc due to phytates); older adults (reduced absorption and dietary intake); people with inflammatory bowel disease, coeliac disease or short bowel syndrome; chronic alcohol users (alcohol impairs zinc absorption and increases urinary excretion); pregnant and breastfeeding women (increased demand); people on long-term medications including diuretics, ACE inhibitors and some antacids.

Zinc and immune function

Zinc is one of the most studied micronutrients for immunity. It is essential for the development and activation of T-lymphocytes, natural killer cells, and neutrophils. Even mild zinc deficiency reduces immune response. Zinc lozenges are widely studied for reducing the duration of common colds: evidence suggests they work best when taken within 24 hours of symptom onset.

Questions to ask your doctor

  • Should my zinc be tested fasting in the morning for accuracy?
  • Could my hair loss or poor wound healing be zinc-related?
  • Do I need zinc supplementation, and what dose is safe?
  • Does my diet or medication affect zinc absorption?

Frequently asked questions

Should a borderline Zinc result be repeated?
Usually. A value just outside the interval is common in people who are entirely well, since about one in twenty healthy results falls outside any 95% reference range by construction. A borderline Zinc is normally rechecked rather than acted on.
What is worth asking a doctor about an abnormal Zinc?
Whether it needs repeating, whether a medicine or recent illness explains it, how far outside the range it actually falls, and whether it changes management or simply needs watching. Those four questions cover most of what matters.
Does Zinc need to be measured fasting?
That depends on the rest of the panel. Samples are usually drawn together and the fasting rule is set by the strictest test included, not by Zinc alone. Follow whatever instruction you were given when the test was arranged.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

  1. Zinc Deficiency. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK493231
  2. Mburu ASW, Thurnham DI, Mwaniki DL, Muniu EM, Alumasa FM. The influence of inflammation on plasma zinc concentration in apparently healthy, HIV+ Kenyan adults and zinc responses after a multi-micronutrient supplement. Eur J Clin Nutr. 2010;64(5):510–7. PMID 20216563 · doi:10.1038/ejcn.2010.33
  3. Wessells KR, Hess SY, Ouédraogo ZP, Rouamba N, Ouédraogo JB, Brown KH. Asymptomatic malaria infection affects the interpretation of biomarkers of iron and vitamin A status… but does not affect plasma zinc concentrations among young children in Burkina Faso. J Nutr. 2014;144(12):2050–8. PMID 25411038 · doi:10.3945/jn.114.200345

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Medical Disclaimer: This page is for general educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis, treatment, and personalised advice.