Zinc
Also known as: Serum Zinc, Zn
What Does Zinc Measure?
Zinc is an essential trace mineral measured in the blood to assess the body's zinc status. A serum or plasma zinc test measures the concentration of zinc circulating in the bloodstream, typically expressed in micrograms per deciliter (mcg/dL) or micromoles per liter (µmol/L). Zinc is found in virtually every cell of the body and plays a critical role in hundreds of enzymatic reactions, making it one of the most functionally important minerals in human biology.
Why Does Zinc Matter?
Zinc is vital for immune function, wound healing, DNA synthesis, cell division, protein synthesis, and normal growth and development. It also supports the senses of taste and smell and is required for the proper function of over 300 enzymes. Adequate zinc levels are especially important during pregnancy, childhood, and adolescence when rapid growth is occurring. Both deficiency and excess can have significant health consequences — deficiency is among the most common micronutrient deficiencies worldwide and is associated with impaired immunity, delayed wound healing, growth retardation, and cognitive dysfunction, while toxicity can cause nausea, immune suppression, and copper deficiency.
Normal Ranges
Males
70–120 mcg/dL (10.7–18.4 µmol/L)
Females
65–120 mcg/dL (9.9–18.4 µmol/L)
Children
Varies by age: typically 60–110 mcg/dL (9.2–16.8 µmol/L)
Causes of High Levels
- Zinc supplementation or overuse of zinc-containing products (e.g., lozenges, denture cream)
- Occupational or environmental zinc exposure (industrial inhalation or ingestion)
- Hemolysis (red blood cell breakdown releasing intracellular zinc into serum)
- Sample contamination from rubber stoppers or collection tubes containing zinc
- Rare genetic conditions affecting zinc transport and metabolism
- Prolonged use of zinc-fortified foods or parenteral nutrition with excess zinc
Causes of Low Levels
- Inadequate dietary intake, particularly in vegetarian or vegan diets low in animal protein
- Malabsorption syndromes such as Crohn's disease, celiac disease, or short bowel syndrome
- Chronic alcoholism, which impairs zinc absorption and increases urinary zinc excretion
How to Improve Your Zinc
Diet
- Eat zinc-rich animal proteins such as oysters (highest known food source), beef, pork, and chicken
- Include shellfish like crab and lobster, which are excellent zinc sources
- Consume legumes, nuts (especially cashews and almonds), and seeds (pumpkin seeds) as plant-based zinc sources
- Soak, sprout, or ferment legumes and grains to reduce phytate content and improve zinc bioavailability
- Pair plant-based zinc sources with vitamin C-rich foods to enhance absorption
Supplements
- Zinc gluconate or zinc citrate: 15–30 mg elemental zinc per day for mild deficiency (well-tolerated forms)
- Zinc picolinate: 15–30 mg per day, considered highly bioavailable and commonly recommended
- If taking zinc long-term, supplement with 1–2 mg of copper daily to prevent copper depletion
- Zinc lozenges (10–13 mg per lozenge) may support immune function during illness but should not be used chronically
- Always take zinc supplements with food to reduce nausea and gastrointestinal upset
Related Biomarkers
Frequently Asked Questions
What are the symptoms of low zinc levels?
Common symptoms of zinc deficiency include frequent infections due to impaired immune function, slow wound healing, hair loss, loss of taste or smell, diarrhea, skin rashes or dermatitis, and poor appetite. In children, deficiency can cause growth retardation and delayed sexual maturation. Since zinc is involved in so many bodily processes, deficiency symptoms can be wide-ranging and nonspecific, which is why a blood test is important for accurate diagnosis.
Is serum zinc an accurate measure of body zinc status?
Serum zinc is the most widely used clinical test for zinc status, but it has limitations. Only about 0.1% of total body zinc circulates in the blood, and serum levels can remain normal even when tissue zinc is depleted. Levels can also be artificially lowered by inflammation, stress, infection, or recent meals. For this reason, serum zinc is best interpreted alongside clinical symptoms, dietary history, and other laboratory markers such as alkaline phosphatase (a zinc-dependent enzyme).
Can you have too much zinc?
Yes, zinc toxicity is possible, usually from excessive supplementation rather than diet alone. Acute toxicity can cause nausea, vomiting, stomach cramps, and diarrhea. Chronic excessive zinc intake (above 40 mg/day for adults over extended periods) can suppress copper absorption, leading to copper deficiency and associated anemia and neurological symptoms. It can also suppress immune function — the opposite of its intended effect at normal doses. Always stay within recommended dosages unless directed by a healthcare provider.