Vitamins & minerals
Selenium
LOINC 5697-2 · mcg/L
Ranges
Reference range: 70–150 mcg/L
What it is
Selenium is a trace mineral that acts as an antioxidant and supports thyroid and immune function.
Why it matters
The test checks selenium status, which matters for thyroid health and protection from oxidative stress.
What high values can mean
A higher value can result from high supplement intake and, in excess, can cause toxicity.
What low values can mean
A lower value can occur with poor intake or certain conditions and may affect thyroid and immune function.
How to improve it
Most people get enough from a varied diet; supplements should be used cautiously and under guidance.
Food & lifestyle
Brazil nuts, seafood, eggs and whole grains are good sources; just a couple of Brazil nuts can be plenty.
Preparing for the test
A blood test; fasting is not usually required — follow your lab's instructions.
When to talk to a doctor
Discuss a low or high selenium with a doctor before changing supplements.
Related markers
Sources
- NIH Office of Dietary Supplements
- MedlinePlus (NIH)
Content reviewed on June 26, 2026
Medical disclaimer
This content is for educational purposes only. It is not medical advice and does not diagnose, treat, or prevent any condition. Reference ranges vary between laboratories — always use the range printed on your report and discuss your results with a healthcare professional.
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