Selenium test: what the blood result means

Selenium is a trace element that the body needs in small amounts, but which is essential for vital functions. From selenium the body makes special proteins — antioxidant enzymes that help protect cells from damage. Researchers are also looking into whether selenium could help protect against certain forms of cancer and reduce the toxic effect of heavy metals, but more research is still needed in this area. Taking a selenium supplement in addition to food sources of selenium is not currently recommended for these purposes. Selenium is obtained from food — Brazil nuts, fish, seafood, red meat, grains, eggs, chicken, liver, garlic, brewer's yeast, wheat germ and enriched bread. The amount of selenium in the blood or in tissues is tested less often than other trace elements — most often when a deficiency is suspected because of long-term artificial feeding or a digestive disorder, or when an excess is suspected. Because a large part of the data on selenium comes from nutrition and toxicology studies rather than from standardised laboratory reference ranges, the interpretation of this marker usually depends on the particular clinical context and should be discussed with a doctor.

• When a person is fed intravenously (parenterally) over a long period — to make sure that selenium stores have not fallen
• When there is a severe disorder of the digestive tract that interferes with the absorption of nutrients, for example Crohn's disease
• When selenium deficiency is suspected because of muscle or heart symptoms, and other causes have already been ruled out
• When an excess of selenium (selenosis) is suspected — hair loss, nail changes, nausea, irritability or tiredness have been noticed, especially while taking food supplements
• When monitoring the diet of people whose diet has been restricted or unbalanced over a long period

The reference range for selenium

Standardised laboratory reference ranges for the amount of selenium in blood, with specific µg/l figures, are not something we can currently confirm from a reliable source. You will find your own laboratory's exact reference interval on your result sheet (see how to read blood test results) — it is worth discussing it with your doctor. The MedlinePlus figures below are amounts of selenium taken in with food, not levels measured in the blood.

A raised amount of selenium is linked to selenosis — a condition that shows itself as hair loss, nail changes, nausea, irritability, tiredness and mild nerve damage. According to MedlinePlus, an excess of selenium is rare in the US.

What can raise selenium

• Too much selenium from food supplements
• A raised amount of selenium in the environment or in certain regions (rarely, but possible)

Symptoms that can accompany a raised level

• Hair loss
• Nail changes
• Nausea
• Irritability
• Tiredness
• Mild nerve damage

What is usually assessed alongside a raised result

• Whether food supplements containing selenium are being taken — it is worth mentioning them to your doctor
• Whether the symptoms (changes to hair or nails) appeared recently and coincide with the start of taking the supplements
• When to repeat the test, so that the change is visible after the supplements have been stopped

A reduced amount of selenium is linked to three diseases: Keshan disease (damage to the heart muscle), Kashin-Beck disease (a disease of the joints and bones) and myxoedematous endemic cretinism. According to MedlinePlus, selenium deficiency is rare in the US — it can follow long-term intravenous feeding or severe digestive disorders.

What can lower selenium

• Long-term intravenous feeding (parenteral nutrition)
• Severe disorders of the digestive tract that interfere with absorption, for example Crohn's disease

Signs that can accompany a low level

• Damage to the heart muscle (Keshan disease)
• A disease of the joints and bones (Kashin-Beck disease)

What is usually assessed alongside a low result

• Whether there is a disease of the digestive tract that interferes with the absorption of nutrients
• Whether the person is fed intravenously over a long period, and whether selenium is included in the nutrition plan
• An assessment of the condition of the heart and the muscles, if Keshan disease is suspected
• When to repeat the test to assess the change

Related pages on this site

• Iodine test
• Zinc test
• Copper test
• Magnesium test
• TSH test