Selenium: What Your Result Means

What is Selenium?

Selenium is a component of antioxidant enzymes and is essential for thyroid hormone function. Soil content drives its presence in food, so levels vary by geography. Testing is ordered when deficiency or toxicity is suspected — it is not part of routine screening for healthy people.

Typical reference interval: Normal serum selenium is commonly roughly 60–150 mcg/L (assays vary; some use ng/mL). Values below the lab's range suggest deficiency; values well above it point to excess from supplements or environmental sources.. Laboratories differ — the interval printed on YOUR report always governs.

If your Selenium is high

Common reasons Selenium runs above the reference interval:

• Supplement overuse — selenium supplements are the usual cause of high levels — some products push blood values well above normal
• High-selenium soil or water — living in seleniferous areas or eating produce grown there raises intake
• Occupational exposure — some industrial settings involve selenium exposure

If your Selenium is low

Common reasons Selenium runs below the reference interval:

• Low soil selenium in food supply — the most common cause — regions with selenium-poor soils produce low-selenium crops
• Restricted diet — very limited or highly processed diets can fall short
• Kidney disease or dialysis — some kidney conditions and treatments lower selenium
• Malabsorption — gut conditions that impair absorption of minerals
• Severe illness — prolonged illness depletes several trace minerals including selenium

Symptoms worth knowing

Deficiency shows up as muscle weakness or pain, fatigue, brain fog, and sometimes hair or nail changes; it can worsen thyroid problems in at-risk people. Excess (from supplements) can cause a garlic odor, nail brittleness, and in high doses, more serious effects.

What usually happens next

1. A low selenium with muscle or thyroid symptoms warrants dietary review and clinician guidance — not random supplementation
2. Interpret selenium with thyroid status, since the two interact
3. If supplements are the suspected cause of high levels, stopping them usually normalizes things quickly

Frequently asked questions about Selenium results