To measure the amount of zinc in the blood (serum/plasma) in order to identify/diagnose deficiency or to monitor response to supplementation
When you have symptoms that may suggest zinc deficiency e.g hair loss, poor wound healing
No test preparation is needed (although fasting results are preferred as zinc concentrations can decrease after meals)
This test measures the amount of zinc in the serum/plasma/urine. Zinc is an essential trace element with important functions throughout the body. Zinc is important for protein synthesis, enzyme function and plays a structural role in proteins and nucleic acids.
Zinc is a component of many high protein foods such as meat, fish and dairy products. It is present in vegetables and grains but the bioavailability is reduced because dietary fibres can inhibit its absorption.
Approximately 20-30% of ingested zinc is absorbed in the small intestine. Zinc is transported in the plasma bound to albumin (~80%) and α2-macroglobulin (~20%). The major route of zinc excretion is via the faeces with little being lost in urine, sweat and other bodily secretions.
Zinc is present in many tissues throughout the body but is not stored at any particular site. Therefore in anabolic states where zinc requirements exceed intake, or where poor absorption occurs, zinc deficiency can result.
Zinc deficiency can present clinically with hair loss, poor wound healing, dermatitis and impaired immune function. In children zinc deficiency can cause growth retardation.
Conditions commonly associated with zinc deficiency include: Alcoholism, pregnancy & burns.
Acrodermatitis enteropathica is an inherited disorder of zinc metabolism/absorption. Zinc deficiency can be treated by supplementation and leads to improvement of clinical symptoms.
How is the sample collected for testing?
A blood sample is taken from a vein in the arm and/or a urine sample (preferably 24h collection) is provided.
Is any test preparation needed to ensure the quality of the sample?
Haemolysis (red blood cell rupture that occurs when the sample is taken) should be avoided as red blood cells contain ~10x the amount of zinc than that of plasma/serum. Fasting samples may be preferred as plasma/serum zinc concentrations have been shown to decrease after eating meals.
How is it used?
Zinc testing is used to investigate for zinc deficiency. It is also useful for monitoring a person who is being nutritionally supplemented to ensure adequate concentrations are achieved.
Zinc can be tested along with other trace elements (e.g iron, copper & selenium) to identify deficiencies where a person may benefit from supplementation.
When is it requested?
When a person displays clinical symptoms that may be associated with zinc deficiency, the measurement of zinc can determine if supplementation is required. Where supplementation is necessary the measurement of zinc can be used to assess when adequate concentrations are achieved.
What does the test result mean?
Zinc decreases in response to infections so a low result may not necessarily mean a person is zinc deficient. Results should be interpreted with clinical symptoms and clinical history.
Since zinc is transported mainly bound to albumin it can be useful to interpret zinc results alongside albumin concentration . For example a low zinc concentration with a normal albumin can suggest zinc deficiency, whereas a low zinc with a low albumin concentration can suggest an acute phase response to infection and not necessarily zinc deficiency.
High results are rarely seen as excess zinc can be excreted in the urine/faeces. Excessive supplementation of zinc can be toxic to the kidneys. Symptoms of zinc toxicity include nausea, vomiting, lethargy and drowsiness.
Is there anything else I should know?
Medications such as steroids & oral contraceptives can reduce circulating concentrations of zinc. Pregnancy is associated with low zinc concentrations due to increased circulating hormones in the body.
Medications such as antibiotics and iron may compete with zinc for intestinal absorption if taken together orally.
Should everyone’s zinc concentrations be measured to check for deficiency?
General screening for zinc deficiency is not recommended. If a person displays clinical symptoms that might be related to zinc deficiency then the measurement of zinc may be useful to assess whether supplementation is recommended.
When is it recommended to measure urine zinc concentrations?
The measurement of urine zinc may be useful for patients on total parenteral nutrition (nutrition that is delivered directly into the blood/bypassing the oral route) who fail to respond to supplementation, in order to assess any excessive losses in the urine.
Should I be taking zinc supplements?
Most individuals have an adequate supply of zinc in their diet and supplementation is not necessary. However, if you have any concerns please consult your GP who can investigate any symptoms and advise if testing is required.