Selenium Testing: Importance, Levels, and Health Impact

What Is Selenium?

Selenium is an essential trace element that plays a crucial role in several bodily functions. 

It supports thyroid hormone production, strengthens the immune system, and acts as a powerful antioxidant. 

The body requires only small amounts of selenium, but both deficiency and excess can lead to health issues.

Doctors may use these tests to detect deficiencies, monitor supplementation, or check for toxicity caused by excessive intake.

When Is Selenium Testing Recommended?

Selenium tests are prescribed when there is a suspicion of deficiency or toxicity. 

They may also be used to monitor selenium levels in individuals at risk due to medical conditions, dietary habits, or environmental exposure.

Testing may be recommended in the following situations:

• Symptoms of selenium deficiency, such as muscle weakness, fatigue, or hair loss, are present.
• Signs of selenium toxicity appear, including nausea, brittle nails, or neurological issues.
• Total parenteral nutrition (TPN) is being administered, requiring selenium intake monitoring.
• Underlying conditions affect the absorption of trace minerals.
• Living in an area with selenium-poor soil, which can lead to lower dietary intake.
• Occupational exposure to selenium occurs in industries like glass manufacturing, electronics, or metalwork.

How Is Selenium Testing Conducted?

Selenium is primarily measured through blood tests, but other methods can provide additional insights.

Types of Selenium Tests:

• Blood Test: Measures selenium levels in serum or plasma, offering the most reliable assessment of current selenium status.
• Urine Test: Reflects recent selenium intake and is useful for monitoring excessive exposure.
• Hair Analysis: Provides information on long-term selenium exposure but is not commonly used in clinical settings.
• Nail Analysis: Offers a long-term selenium assessment similar to hair testing.

Tests That Include Selenium Measurement:

Selenium levels may be assessed alongside other trace minerals in panels such as:

• Trace Element Panel: Measures multiple essential minerals, including selenium, zinc, and copper.
• Comprehensive Metabolic Panel (CMP): May include selenium testing if needed for diagnosis.

Special Preparations for Selenium Testing:

• No fasting is required for a selenium blood test.
• Selenium supplements should be avoided before testing unless instructed otherwise.
• Any potential exposure to high selenium levels at work or through diet should be reported to the healthcare provider.

What Are the Normal Selenium Levels?

Normal selenium levels vary depending on the laboratory and the testing method used. The typical reference ranges for adults are:

• Blood Selenium Levels: 150-241 ng/mL (nanograms per milliliter).
• Urine Selenium Levels: 5.5 - 106 µg/L (micrograms per liter).

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used.

What Do Abnormal Levels Mean?

High Selenium Levels

Excess selenium in the body can result from over-supplementation, excessive dietary intake, or environmental exposure. High selenium levels may lead to toxicity, causing various symptoms.

Possible causes of high selenium levels:

• Overuse of Supplements: Taking high doses of selenium supplements can cause toxicity.
• Dietary Excess: Consuming large amounts of selenium-rich foods like Brazil nuts may lead to elevated levels.
• Occupational Exposure: Industries like glass manufacturing, metalwork, and electronics may expose workers to high selenium levels.
• Medical Treatments: Some treatments or dietary programs may lead to increased selenium intake.

• Reduce selenium-rich foods in the diet.
• Stop or lower selenium supplement intake (under medical supervision).
• Avoid occupational exposure by using protective equipment.
• Drink plenty of water to aid selenium elimination through urine.
• Seek medical advice if symptoms of toxicity appear.

Low Selenium Levels

A deficiency in selenium can weaken immune function, slow metabolism, and increase the risk of certain diseases. Low levels often result from poor dietary intake or absorption issues.

Possible causes of low selenium levels:

• Poor Diet: Low intake of selenium-rich foods like seafood, nuts, and meat can lead to deficiency.
• Digestive Disorders: Conditions like Crohn’s disease or celiac disease may impair selenium absorption.
• Chronic Illnesses: Kidney disease and some cancers can reduce selenium levels in the body.
• Geographic Deficiency: Some regions have selenium-poor soil, affecting the selenium content in locally grown foods.

• Include more selenium-rich foods such as seafood, meat, eggs, and Brazil nuts.
• Consider selenium supplements if recommended by a healthcare professional.
• Address underlying health conditions affecting mineral absorption.
• Monitor selenium intake if living in a region with selenium-poor soil.

Which Specialist Should Be Consulted?

If selenium levels are abnormal, the appropriate specialist depends on the symptoms and underlying health concerns:

• Primary Care Doctor: First point of contact for general selenium-related concerns.
• Endocrinologist: If selenium imbalance affects thyroid function.
• Gastroenterologist: If digestive issues impact selenium absorption.
• Toxicologist: If selenium toxicity is suspected due to occupational exposure or overuse.