How to tell if your selenium is low?

January 7, 2026 •

4 min read

Millions of individuals worldwide are affected by insufficient selenium intake, a common issue with far-reaching health implications. Learning how to tell if your selenium is low is key to recognizing potential symptoms like fatigue and hair loss, and seeking proper diagnosis.

Quick Summary

This article explores the common indicators of low selenium, such as a weakened immune system, thyroid dysfunction, and fatigue. It also discusses the primary risk factors, how a doctor can diagnose a deficiency, and effective treatment options.

Key Points

Persistent Fatigue: Unexplained and chronic tiredness can be a key symptom of low selenium due to its role in energy metabolism.
Hair and Nail Health: Brittle nails and thinning or loss of hair are common signs of a selenium deficiency.
Thyroid Problems: Since selenium is concentrated in the thyroid, a lack of it can lead to dysfunction and symptoms of hypothyroidism, such as weight changes and mood swings.
Weakened Immunity: A compromised immune system, resulting in more frequent infections, can indicate insufficient selenium levels.
Professional Diagnosis is Key: Symptoms alone are not definitive. A blood test or a functional test of glutathione peroxidase is needed for accurate diagnosis.
Dietary Sources: Eating Brazil nuts, seafood, meat, and eggs is the primary way to get more selenium from food.
Supplementation for Severe Cases: In cases of confirmed severe deficiency, supplements like selenomethionine may be prescribed under medical supervision.

The Critical Role of Selenium in the Body

Selenium is a vital trace mineral that plays an essential part in numerous bodily functions, influencing our metabolism, immune system, and overall health. It is a key component of selenoproteins, which act as powerful antioxidants, protecting cells from damage caused by free radicals. A deficiency can impair these enzymes, affecting everything from thyroid function to reproductive health. However, because the symptoms are often non-specific, identifying a deficiency can be challenging without proper medical evaluation.

Primary Signs and Symptoms of Low Selenium

Spotting a selenium deficiency often starts with noticing persistent, subtle changes in your health. While these signs can overlap with other conditions, their presence should prompt a conversation with a healthcare provider.

Persistent Fatigue and Muscle Weakness

One of the most frequently reported symptoms of low selenium is chronic fatigue and general weakness that doesn't improve with rest. Selenium is involved in energy metabolism and muscle function, so a lack of it can lead to noticeable dips in your energy levels and cause muscle pain, tenderness, and cramps.

Hair and Nail Changes

Selenium plays a role in keratin synthesis, which is crucial for healthy hair and nails. A deficiency can manifest as:

Thinning or hair loss
Discolored or brittle nails
White spots on the fingernails

Thyroid Dysfunction

The thyroid gland has the highest concentration of selenium per gram of tissue in the body. Selenium is vital for converting the inactive thyroid hormone (T4) into its active form (T3). A deficiency can impair this conversion, leading to symptoms of hypothyroidism, such as:

Weight gain
Sensitivity to cold
Exhaustion
Mood swings

Weakened Immune System

Selenium is a powerful supporter of immune function, essential for the proper proliferation of T-cells and other immune cells. An inadequate supply can compromise your body's defenses, making you more susceptible to frequent colds, flu, and infections.

Cognitive and Mood Issues

Research has indicated a connection between low selenium levels and certain neurological functions and mood regulation. Some people with a deficiency may experience:

Mental fog or difficulty concentrating
Anxiety and depression
Overall cognitive decline

Who is at Risk for Selenium Deficiency?

While selenium deficiency is relatively uncommon in places like the United States due to varied food sources, certain populations are more vulnerable. Key risk factors include:

Geographic location: Some regions, particularly parts of Europe and China, have selenium-poor soil. People whose diets primarily consist of locally grown produce are at higher risk.
Dietary choices: Individuals following vegetarian or vegan diets often have lower selenium intakes, as animal products are typically rich sources.
Medical conditions: Certain digestive disorders, such as Crohn's disease or celiac disease, can impair nutrient absorption.
Chronic illness: Conditions like HIV/AIDS and kidney dialysis can lead to lower selenium levels.
Pregnancy and lactation: Increased demand for the mineral during these periods can put women at risk.

How to Diagnose Low Selenium

Due to the non-specific nature of symptoms, a medical diagnosis is essential to confirm a selenium deficiency. Several methods are used to assess a person's selenium status:

Blood Tests

Serum or plasma selenium levels: This measures recent selenium intake, providing a snapshot of current levels.
Whole blood selenium: This indicates long-term status over months or years, as it includes selenium stored in red blood cells.

Functional Biomarker Tests

Glutathione peroxidase (GPX) activity: This test measures the activity of this selenium-dependent enzyme. If the level is low, it can indicate insufficient selenium.

Tissue Analysis

Hair or nail samples: These can also be analyzed to indicate long-term selenium intake over a longer period.

A Comparison of Selenium Diagnostic Methods


Diagnostic Method	Reflects	Best Used For	Limitations
Serum/Plasma Test	Recent intake	Screening for acute deficiency	Fluctuates based on recent diet, may be affected by inflammation
Whole Blood Test	Long-term status	Assessing status over months/years	Requires careful interpretation; less common than serum tests
Glutathione Peroxidase (GPX) Activity	Functional status	Indicating functional deficiency	Can be influenced by inflammation and oxidative stress
Hair/Nail Analysis	Long-term intake	Population-level monitoring	Results can vary widely and may not be reliable for individual diagnosis

Managing and Treating Selenium Deficiency

Addressing a deficiency typically involves a two-pronged approach: dietary changes and, if necessary, supplementation. It is crucial to consult a healthcare provider before starting any supplement regimen to ensure proper dosage and avoid toxicity.

Excellent Dietary Sources of Selenium

Brazil Nuts: The single most potent source; just one nut a day may satisfy the daily requirement.
Seafood: Tuna, sardines, halibut, and cod are excellent sources.
Meat and Poultry: Beef, turkey, and chicken breast are good options.
Eggs: A reliable source of selenium.
Organ Meats: Liver and kidney are particularly high in the mineral.
Seeds: Sunflower seeds and chia seeds provide a solid plant-based option.

The Role of Supplements

For moderate to severe deficiencies, a doctor may recommend supplements. These are available in forms like selenomethionine and sodium selenite. Selenomethionine is generally considered easier for the body to absorb. Supplementation can restore optimal levels, but regular follow-up with a healthcare provider is important. For more on the medical context of selenium, see this NCBI Bookshelf: Selenium Deficiency.

Conclusion

Understanding how to tell if your selenium is low is a crucial step towards maintaining good health. The symptoms, though varied and often subtle, can provide clues to an underlying deficiency. With key indicators like fatigue, weakened immunity, and hair changes, it is important to consult a healthcare provider for an accurate diagnosis through blood or functional tests. Addressing a deficiency with dietary adjustments and medical-guided supplementation can help restore proper bodily function and prevent more serious long-term health consequences.

Frequently Asked Questions

Common symptoms include persistent fatigue, muscle weakness or pain, hair loss, brittle or discolored nails, a weakened immune system leading to frequent infections, and impaired thyroid function.

A doctor can test your selenium levels through a blood test, which can measure recent intake or long-term status, or by measuring the activity of the selenium-dependent enzyme glutathione peroxidase.

Brazil nuts are an exceptionally rich source. Other great dietary sources include seafood (like tuna and sardines), meats, eggs, organ meats, sunflower seeds, and whole grains.

If left untreated, a selenium deficiency can increase the risk of serious health issues, including cardiovascular diseases, worsened immune function, cognitive decline, and fertility problems.

Individuals at a higher risk include those living in areas with selenium-poor soil, vegans and vegetarians, people with digestive disorders like Crohn's disease, patients on kidney dialysis, and those with chronic illnesses.

Yes, supplements can help correct a deficiency, but they should only be taken under medical supervision. Excessive intake can cause toxicity, so consulting a healthcare provider for the correct dosage is crucial.

The thyroid requires selenium to function properly, particularly to produce active thyroid hormones. A deficiency can lead to thyroid dysfunction and exacerbate conditions like hypothyroidism.

Yes, selenium toxicity (selenosis) can occur from excessive intake, especially from supplements. Symptoms of an overdose can include a garlic-like breath odor, hair loss, and brittle nails.