--- title: "What does a low Selenium mean?" type: biomarker-interpretation url: "https://www.test-well.com/biomarkers/selenium/low" biomarker: Selenium direction: low reference_range: - "age 18+: 70.0 – 150 mcg/L" reviewed_at: 2026-09-08 review_status: reviewed date_published: 2026-09-05 --- # What does a low Selenium mean? > Low selenium reflects intake — soil selenium varies by region, and people eating mainly locally grown food in low-selenium areas, on restricted or long-term tube-fed diets, or with malabsorption run low — plus higher needs in dialysis, HIV and critical illness. Selenium supports thyroid hormone activation and antioxidant enzymes; deficiency is linked to hypothyroidism symptoms, muscle weakness, heart muscle disease (Keshan disease) and impaired immunity. Acute inflammation lowers the measured level transiently. ## What is the normal range for Selenium? - age 18+: 70.0 – 150 mcg/L Can reflect malabsorption or low-selenium diets in certain regions. ## What are the common causes of low Selenium? 1. Low dietary intake (low-selenium soils, restrictive or vegan diets without Brazil nuts, seafood or grains from selenium-rich regions) 2. Malabsorption: celiac disease, Crohn's, bariatric surgery, short bowel 3. Long-term parenteral or enteral nutrition without selenium 4. Kidney disease on dialysis, HIV, critical illness 5. Phenylketonuria and other medically restricted diets 6. Acute inflammation (transient false low) ## What symptoms go with low Selenium? - Often none - Fatigue, muscle weakness or pain, hair loss, whitened nail beds - Symptoms of low thyroid function, frequent infections - Heart failure symptoms in severe long-standing deficiency ## What do clinicians usually check next? - Repeat when well (CRP alongside) - TSH and Free T4/Free T3 - Dietary review — a few Brazil nuts a week or seafood usually suffices; supplements are dosed to avoid excess (upper limit 400 mcg/day) Follow-up tests at TestWell: [TSH (Thyroid Stimulating Hormone)](https://www.test-well.com/tests/tsh) ($26.99), [TSH + Free T4](https://www.test-well.com/tests/tsh-with-free-t4) ($27.99), [Free T3 (Triiodothyronine)](https://www.test-well.com/tests/free-t3) ($30.99), [C-Reactive Protein (CRP)](https://www.test-well.com/tests/crp) ($26.99), [Free T4 (Thyroxine)](https://www.test-well.com/tests/free-t4-test) ($23.99), [T3 Uptake](https://www.test-well.com/tests/t3-uptake-test) ($22.99). ## How do you recheck Selenium? | Test or panel | Type | Price | Fasting | Results | | --- | --- | --- | --- | --- | | [Vitamin & Mineral Deficiency Panel](https://www.test-well.com/tests/vitamin-mineral-panel) | Panel (9 tests) | $189.99 | No | 3–5 business days | | [Men's Hair Health Panel](https://www.test-well.com/tests/mens-hair-health-panel) | Panel (19 tests) | $499.99 | No | 4–7 business days | | [Women's Hair Health Panel](https://www.test-well.com/tests/womens-hair-health-panel) | Panel (19 tests) | $469.99 | No | 4–7 business days | | [Selenium](https://www.test-well.com/tests/selenium) | Test | $64.99 | No | 3–7 business days | Plus one $6 lab processing fee per order; physician authorization included. ## Common questions ### How much selenium do I need? 55 mcg a day for adults. One Brazil nut can supply that or more, which is also why taking Brazil nuts plus a supplement is the usual route to excess (hair loss, brittle nails, garlic breath). ## Related - [Selenium reference ranges](https://www.test-well.com/biomarkers/selenium) - [Glucose reference range](https://www.test-well.com/biomarkers/glucose) - [Creatinine reference range](https://www.test-well.com/biomarkers/creatinine) - [eGFR reference range](https://www.test-well.com/biomarkers/egfr) ## Sources - [Mayo Clinic Labs](https://www.mayocliniclabs.com/test-catalog/overview/82382) - [NIH Office of Dietary Supplements — Selenium fact sheet](https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/) --- Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-08. Review policy: https://www.test-well.com/editorial-policy Canonical page: https://www.test-well.com/biomarkers/selenium/low Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.