Selenium levels: what's normal, high and low
An antioxidant trace mineral important for thyroid function and immune health.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Selenium is measured with a standard blood draw; no fasting is needed. A typical reference range is 70.0 – 150 mcg/L. At TestWell it's $64.99 all-in as Selenium, results in 3–7 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- mcg/L / ug/L
- Sample
- Blood draw
- Fasting
- Not required
- Results
- 3–7 business days
- Price
- $64.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Selenium Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+ | 70.0 – 150 mcg/L |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
Have a result in hand? analyze it with your AI assistant using these reviewed ranges, or run it through our explainer. Tools: look up another marker's range · convert lab units
What your Selenium result may mean
Can reflect malabsorption or low-selenium diets in certain regions.
What a low Selenium means: causes, symptoms, next steps ↓Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
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.
Common causes of a low Selenium
- Low dietary intake (low-selenium soils, restrictive or vegan diets without Brazil nuts, seafood or grains from selenium-rich regions)
- Malabsorption: celiac disease, Crohn's, bariatric surgery, short bowel
- Long-term parenteral or enteral nutrition without selenium
- Kidney disease on dialysis, HIV, critical illness
- Phenylketonuria and other medically restricted diets
- Acute inflammation (transient false low)
Ordered from most to least common.
Symptoms that can go with it
- 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 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) ($26.99), TSH + Free T4 ($27.99), Free T3 (Triiodothyronine) ($30.99), C-Reactive Protein (CRP) ($26.99), Free T4 (Thyroxine) ($23.99), T3 Uptake ($22.99).
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).
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
How do you get a Selenium test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Selenium is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Selenium | This marker only | $64.99 |
| Vitamin & Mineral Deficiency Panel | 9 tests | $189.99 |
| Total Body Essentials Panel | 39 tests | $399.99 |
| Women's Hair Health Panel | 19 tests | $469.99 |
| Men's Hair Health Panel | 19 tests | $499.99 |
Quest vs. Labcorp for Selenium: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $64.99 |
| Labcorp | Yes | $77.99 |
| BioReference (NY & NJ) | Yes | $64.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Frequently asked
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.
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).
Do I need a doctor's order to test my selenium?
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
How long does it take to get Selenium results?
Most Selenium results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.
How much does a Selenium test cost?
Our Selenium starts at $64.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.
Do I need to fast before my Selenium test?
Fasting is not required for the Selenium test. You can have your blood drawn any time of day.
Which lab will process my Selenium test?
Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.
Ready to test your selenium?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $64.99.