Zinc is an important trace mineral required for numerous bodily processes. It supports immune system function, aids in proper wound healing, and is a factor in many enzyme activities. Because of its involvement in DNA and protein synthesis, zinc is particularly important during periods of rapid growth, such as childhood and pregnancy. Measuring zinc status is often required to diagnose nutritional imbalances or underlying health conditions.
Naming and Types of Zinc Tests
The most common blood test ordered to assess zinc status is called the Serum Zinc Test or the Plasma Zinc Test. These names refer to the liquid portion of the blood analyzed after cellular components are removed. The choice between serum and plasma depends on the laboratory’s specific procedures.
Plasma is the liquid portion of the blood containing clotting factors, while serum is the liquid remaining after the blood has clotted. Plasma is often preferred because serum samples can show slightly higher zinc concentrations due to zinc leaking from blood cells during clotting. Regardless of the sample type, the blood must be collected in special trace element-free tubes to prevent external contamination.
While blood tests are the standard method, zinc status can also be assessed through a 24-hour urine collection. However, plasma or serum concentrations remain the most utilized biochemical indicators for quick assessment. Results are usually reported in micrograms per deciliter (µg/dL) or micromoles per liter (µmol/L).
Medical Indications for Testing Zinc Levels
A healthcare provider orders a zinc test when a patient exhibits symptoms consistent with deficiency or has a condition predisposing them to malabsorption. Common reasons for testing include unexplained hair loss, slow-healing wounds, persistent skin lesions, and recurrent infections. Testing is also indicated for patients reporting an altered sense of taste or smell, as zinc is directly involved in these sensory functions.
Conditions that affect nutrient absorption, such as Crohn’s disease, celiac disease, or chronic diarrhea, significantly increase the risk of deficiency and require regular monitoring. Patients who have undergone gastric bypass surgery or receive long-term total parenteral nutrition (TPN) are also routinely tested due to compromised nutrient intake.
Other populations requiring testing include those with chronic liver or kidney disease and individuals who frequently consume alcohol, due to altered zinc metabolism or increased excretion. In children, a blood test may be ordered for delayed growth or developmental issues, as deficiency can impair normal physical development.
Interpreting Zinc Blood Test Results
Interpreting the zinc test involves comparing the measured value to the laboratory’s established reference range. For adults, a typical reference range for serum zinc is between 70 and 120 µg/dL (or 11 to 18.4 µmol/L). A result within this range suggests adequate zinc status.
A value below the normal range indicates a zinc deficiency, caused by insufficient dietary intake, malabsorption, or chronic illnesses that increase mineral loss. Low levels may also be related to inflammation or low albumin levels, since zinc is mostly bound to proteins in the blood. In these cases, the clinical context and other markers are considered alongside the zinc result.
A result above the normal range, known as hyperzincemia, suggests excessive intake, usually from high-dose dietary supplements. Significant excess can disrupt the absorption of other trace minerals, most notably copper, potentially leading to a secondary copper deficiency. Clinical response to a low value involves dietary changes or supplementation, while a high value requires reducing supplement intake.