Understanding Selenium: Normal vs Optimal Ranges

?What is Selenium?

Selenium is an essential trace mineral incorporated into selenoproteins including glutathione peroxidases (antioxidant enzymes), thioredoxin reductase, and iodothyronine deiodinases (required for T4-to-T3 thyroid hormone conversion). Dietary selenium content varies widely by geographic region based on soil selenium levels.

!Why It Matters

Selenium deficiency impairs antioxidant defence, thyroid hormone metabolism, and immune function. It is associated with Keshan disease (cardiomyopathy), Kashin-Beck disease (bone and joint disease), and increased thyroid antibody titres. Selenium supplementation (200 mcg/day) is the best-evidenced nutritional intervention for reducing Anti-TPO antibodies in Hashimoto's thyroiditis.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• Deficiency: muscle weakness, myopathy, fatigue, impaired thyroid function
• Toxicity (selenosis): hair and nail brittleness, garlic breath, neurological symptoms

How to Improve Your Levels

• 1Brazil nuts: just 1-2 per day provides adequate selenium (most potent source)
• 2Seafood, organ meats, and whole grains are good selenium sources
• 3Selenium supplementation for Hashimoto's thyroiditis (200 mcg selenomethionine daily)
• 4Avoid excessive supplementation — selenium is toxic above 400 mcg/day

When to Test

Thyroid disease management; suspected deficiency in geographic selenium-poor areas; malnutrition assessment; Keshan-endemic regions.

Related Biomarkers