Selenium: Nursing Guide
Serum selenium reflects antioxidant status and thyroid-related enzyme function — yet a single value cannot separate inadequate TPN micronutrients from malabsorption, dialysis losses, or recent supplement timing. Mayo notes deficiency is usually below 40 mcg/L and TPN supplementation targets above 70 mcg/L. Nurses verify metal-free collection, contrast timing, and trend results with fatigue, hair loss, and cardiomyopathy cues in long-term TPN or hemodialysis patients without waiting for a “borderline” result to delay dietitian follow-up.
Contents
Quick Facts
Key Takeaway
The main nursing priority with selenium testing is pairing serum trends with TPN or dialysis context, valid metal-free collection, and deficiency or selenosis symptoms — Mayo cites deficiency usually below 40 mcg/L
Specimen & Collection Details
Nurse quick-reference for collection prep that affects result quality.
Royal blue top — trace element, metal-free (serum)
the reporting laboratory specifies royal blue-top trace-element tube, metal-free, for selenium, serum — avoid standard tubes that may contaminate trace-metal results
Serum or plasma (royal blue trace-element tube, metal-free)
the reporting laboratory lists 0.8 mL serum minimum for selenium, serum — follow reporting laboratory requirements
Delay collection at least 96 hours after gadolinium, iodine, or barium contrast per Mayo; document TPN cycle, recent selenium supplements, and dialysis schedule when relevant
Not specified in reviewed NIH ODS or the reporting laboratory references for selenium alone — follow prescriber and local laboratory instructions when paired with fasting panels
Refrigerate serum per Mayo trace-element transport guidance; avoid metal contamination of caps, needles, or collection surfaces
the reporting laboratory cites 1–3 days for selenium, serum — institutional send-out intervals may vary
Trace elements / clinical chemistry or reference laboratory
What is Selenium?
Selenium measures selenium in serum or plasma to assess nutritional status and monitor replacement therapy. the reporting laboratory lists the test for monitoring selenium replacement therapy. NIH ODS notes plasma/serum concentrations of at least 8 mcg/dL (80 mcg/L) are usually sufficient to maximize the activity of selenium-dependent enzymes in adults.
Overview
Nurses encounter selenium when long-term celiac disease or TPN patients develop fatigue, myopathy, or hypothyroidism-like symptoms. NIH ODS notes selenium deficiency is uncommon in the United States but can occur with prolonged TPN without adequate supplementation and in hemodialysis patients. Mayo cites deficiency usually below 40 mcg/L with adult reference 110–165 mcg/L.
On this Tests & Diagnostics page, nursing focus is TPN and dialysis prep, metal-free collection validity, interpretation, selenosis escalation, and teaching — not step-by-step venipuncture technique (see the Performance procedure guide). Pair selenium with TSH trends when thyroid symptoms appear, iron studies when anemia overlaps, and heart failure monitoring when cardiomyopathy is suspected in deficient states.
Before acting on selenium results: confirm TPN or dialysis status, supplement and contrast timing, metal-free collection, and symptom trend. After results return: compare with prior levels (Mayo TPN target above 70 mcg/L), notify prescriber or dietitian when deficiency symptoms align with values below 40 mcg/L, and evaluate outcomes after supplementation — not one draw alone.
TPN Deficiency, Selenosis, and Trace-Element Collection Safety
Long-term TPN and hemodialysis patients can develop clinically significant selenium deficiency while a prior level still looks acceptable — Mayo cites deficiency usually below 40 mcg/L and TPN targets above 70 mcg/L. The highest-risk nursing errors are reassuring teams because U.S. population intake is generally adequate, collecting within 96 hours of contrast, and using non-metal-free tubes that invalidate trace-element results.
- Selenium below 40 mcg/L with fatigue or myopathy on long-term TPN per Mayo guidance
- Declining trend (for example 48 to 32 mcg/L) without TPN formula selenium review
- Selenosis symptoms — hair loss, nail brittleness, garlic breath — with supplement intake above NIH ODS adult UL 400 mcg/day
- Collection within 96 hours of gadolinium, iodine, or barium contrast per Mayo
Document: TPN route and additives, supplement list, contrast timing, metal-free collection, selenium trend, fatigue and weakness findings, dietitian notification, and repeat testing plan.
What Serum Selenium Can and Cannot Tell You
This test can help identify:
- Low or falling serum selenium in TPN, dialysis, or malabsorption when trends and symptoms align
- Response to selenium replacement therapy per Mayo monitoring indication
- Need for dietitian TPN formula review when levels fall below 70 mcg/L supplementation target
- Possible selenosis when chronic supplement intake exceeds NIH ODS tolerable upper limit
This test cannot:
- Diagnose hypothyroidism, cardiomyopathy, or TPN adequacy alone — requires clinical correlation
- Replace dietitian review of TPN micronutrient content and enteral intake
- Rule out deficiency because one prior level was within reference on long-term TPN
- Be valid after recent contrast media without the 96-hour delay per Mayo
Pre-draw Checks for Selenium on Trace-Element Panels
Verify
Clarify before proceeding when:
- Contrast imaging occurred within the past 96 hours
- Standard serum tube requested instead of metal-free trace-element supplies
- TPN selenium content unknown while prior trend is falling
- High-dose selenium supplements taken within 24 hours without documentation
- Symptomatic weakness develops before specimen reaches the laboratory
- Home PN patient cannot confirm cycled TPN schedule or additive list
Reading Selenium With TPN Trends, Dialysis, and Symptoms
Integrate selenium with TPN content, supplement timing, dialysis losses, contrast history, and symptom trends. Mayo adult reference 110–165 mcg/L, deficiency usually below 40 mcg/L, and TPN target above 70 mcg/L are guides — not substitutes for bedside assessment.
| Selenium context (Mayo / NIH ODS) | Clinical meaning | Nursing focus |
|---|---|---|
| ≥80 mcg/L (≥8 mcg/dL) — NIH sufficient example | Usually adequate enzyme activity in adults | Continue scheduled monitoring on TPN or dialysis; still trend serial values |
| Below 40 mcg/L — Mayo deficiency threshold | Supports deficiency when symptoms and TPN/dialysis context fit | Notify prescriber and dietitian; review TPN selenium additive |
| TPN target above 70 mcg/L — Mayo | Supplementation goal during replacement monitoring | Evaluate outcomes after formula change; repeat level per orders |
| Chronic intake above 400 mcg/day — NIH UL | Selenosis risk with hair loss, nail brittleness, garlic breath | Review supplements with prescriber; hold high-dose products per orders only |
Reference ranges, critical values, and protocols may vary by laboratory, institution, patient population, and testing method. Always follow local policy and the reporting laboratory’s reference range.
Contrast Delay, Metal-Free Tubes, and TPN Traps at the Bedside
| Bedside point | Nursing note |
|---|---|
| Contrast trap | 96-hour delay after gadolinium, iodine, or barium per Mayo — reschedule invalid draws |
| Tube trap | Royal blue metal-free only — standard tubes may contaminate trace results |
| TPN trap | Document formula selenium content — deficiency common on prolonged TPN ODS |
| Trend trap | Compare serial levels — fall from 48 to 32 mcg/L matters even if prior value seemed low-normal |
| Selenosis trap | Hair loss and garlic breath with high supplements — NIH UL 400 mcg/day adult |
Why Selenium is Ordered
Selenium testing is ordered to assess nutritional status and monitor replacement in at-risk populations — always integrated with intake, TPN formula review, and symptoms.
| Clinical Indication | What the Test Answers | Nursing Rationale |
|---|---|---|
| Monitoring selenium replacement therapy | Is the patient on long-term TPN, home PN, or chronic dialysis with scheduled micronutrient panels? | the reporting laboratory lists monitoring selenium replacement therapy as a primary indication; NIH ODS notes TPN-related deficiency is a recognized U.S. clinical context. |
| Suspected deficiency with compatible symptoms | Are fatigue, myopathy, hair loss, or hypothyroid-like symptoms present with malabsorption or restricted intake? | NIH ODS links low selenium to Keshan cardiomyopathy risk in deficient regions and describes deficiency features including muscle weakness and thyroid dysfunction. |
| Hemodialysis or CKD micronutrient surveillance | Does the patient dialyze regularly with protocol-driven trace-element monitoring? | NIH ODS notes hemodialysis patients are at increased deficiency risk — selenium trends guide replacement per prescriber and dietitian protocol. |
| Evaluation of suspected selenosis | Is chronic supplement intake above the adult UL (400 mcg/day ODS) with hair loss, nail brittleness, or garlic breath? | NIH ODS cites selenosis above the tolerable upper intake level with characteristic mucocutaneous and breath findings — hold high-dose supplements per prescriber direction. |
Contraindications and Precautions
There is no absolute contraindication to selenium testing when monitoring or deficiency is suspected. Defer non-urgent collection only when immediate instability requires stabilization first — do not delay dietitian or prescriber review when deficiency symptoms and low trends are already documented.
- Serum selenium below 40 mcg/L with worsening fatigue, myopathy, or heart failure symptoms in TPN or dialysis patients per Mayo deficiency guidance — notify prescriber and dietitian per protocol.
- Declining trend (for example 48 to 32 mcg/L) on long-term TPN without formula adjustment — urgent micronutrient review.
- Signs of selenosis — hair loss, nail brittleness, garlic breath, nausea — with supplement intake near or above NIH ODS adult UL 400 mcg/day.
- Gadolinium, iodine, or barium contrast within 96 hours may invalidate trace-element results per Mayo — reschedule or document delay.
- Metal contamination from non-trace tubes or equipment falsely alters selenium — use royal blue metal-free supplies only.
- Recent high-dose selenium supplements may transiently raise serum levels — document dose and timing before interpreting toxicity.
- Selenium below 40 mcg/L with compatible symptoms in TPN, dialysis, or malabsorption.
- Falling trend on serial monitoring despite ongoing replacement orders.
- Selenosis symptoms with excessive supplement use — prescriber and pharmacist review.
Patient Preparation
Preparation focuses on contrast timing, metal-free supplies, TPN and supplement documentation, and symptom baseline — not fasting unless paired tests require it.
Pre-test checksReview selenium supplements, TPN additives, multivitamins, and thyroid medicines — document for interpretation; do not independently change TPN or supplement doses without prescriber or dietitian orders.
Performance — nursing procedure guide
This page is a Tests & Diagnostics guide for Selenium. It emphasizes why the test is ordered, how to interpret results, when to escalate, and preparation factors that affect validity — not step-by-step performance technique (those live under Nursing Procedures when available).
Step-by-step technique, supplies, infection prevention, and immediate post-procedure monitoring for this test are covered in:
Use the Patient preparation, Results and interpretation, and Nursing responsibilities sections on this page for order verification, pre-analytic checks, result follow-up, critical-value escalation, and documentation.
Result follow-up at a glance
Nursing workflow on this page — from order to safe action on results:
Results and Interpretation
Selenium is commonly reported in mcg/L (µg/L). the reporting laboratory cites adult (≥18 y) reference 110–165 mcg/L, deficiency usually below 40 mcg/L, and TPN supplementation target above 70 mcg/L. NIH ODS notes plasma/serum ≥8 mcg/dL (80 mcg/L) usually maximizes enzyme activity. Always use the reporting laboratory reference interval.
Reference ranges, critical values, and protocols may vary by laboratory, institution, patient population, and testing method. Always follow local policy and the reporting laboratory’s reference range.
| Result | Range / Finding | Clinical Meaning | Nursing Action |
|---|---|---|---|
| Within reference interval | Within laboratory reference interval — Mayo adult example 110–165 mcg/L | Selenium adequate for enzyme function when clinical context agrees — NIH ODS cites ≥80 mcg/L as usually sufficient | Continue scheduled monitoring on TPN or dialysis per protocol; document trend |
| Borderline / near reference limit | Between NIH sufficient threshold (~80 mcg/L) and laboratory lower reference | May warrant closer TPN or supplement review when symptoms or downward trend present | Notify dietitian when TPN formula lacks selenium or trend is falling; repeat per orders |
| High / above reference interval | Above reference interval or near NIH adult UL exposure | May reflect excess supplementation — NIH ODS selenosis features include hair loss, nail brittleness, and garlic breath above 400 mcg/day chronic intake | Notify prescriber; review supplement and TPN selenium content; hold high-dose products only per orders |
| Low / below reference interval | Below 40 mcg/L or declining trend (Mayo deficiency guidance) | Supports deficiency in TPN, dialysis, or malabsorption when symptoms align | Notify prescriber and dietitian; coordinate replacement; monitor cardiac and thyroid symptoms |
Critical Selenium Results and Escalation
Institution-specific critical selenium thresholds vary. Mayo cites deficiency usually below 40 mcg/L and TPN targets above 70 mcg/L; NIH ODS describes selenosis above the 400 mcg/day adult upper limit. Urgent nursing action depends on symptoms, trends, and TPN or dialysis context per facility policy.
| Critical Finding | Threshold / Value | Immediate Action |
|---|---|---|
| Selenium below 40 mcg/L with deficiency symptoms | Mayo deficiency threshold with fatigue, myopathy, or cardiomyopathy concern in at-risk patient | Notify prescriber and dietitian immediately; review TPN formula; document read-back; arrange replacement per protocol |
| Declining trend on TPN without formula change | For example fall from 48 to 32 mcg/L over six months on home PN | Urgent dietitian and prescriber review; repeat selenium per orders; evaluate outcomes after supplementation adjustment |
| Selenosis symptoms with high supplement intake | Hair loss, nail brittleness, garlic breath, GI upset with chronic intake above NIH UL | Hold supplements per prescriber; notify team; monitor symptoms; repeat level per protocol |
Stop routine workflow and escalate according to facility policy when selenium is below Mayo deficiency thresholds with compatible symptoms, when TPN trends fall without intervention, or when selenosis features appear with excessive intake.
Factors Affecting Results
Selenium interpretation depends on TPN content, supplement timing, dialysis losses, contrast interference, and collection quality.
- Recent high-dose selenium supplement before draw elevating serum transiently
- Metal contamination from non-trace collection supplies
- Laboratory error or wrong patient specimen — always verify identifiers
- Draw within 96 hours of gadolinium, iodine, or barium contrast per Mayo invalidating result
- Single “adequate” level while TPN formula lacks selenium — trend may still fall
- Assuming U.S. population adequacy without TPN or dialysis context ODS
- Contrast media within 96-hour collection window
- Non-metal-free tubes or contaminated needles
- Hemolysis or delayed transport affecting assay validity
Serum selenium reflects recent status but does not alone diagnose cardiomyopathy, hypothyroidism, or TPN adequacy. NIH ODS notes U.S. deficiency is uncommon outside TPN, dialysis, and malabsorption contexts. Always interpret with trends, intake, TPN review, and symptoms — evaluate outcomes after replacement, not one value alone.
Nursing Responsibilities
Nursing responsibilities center on valid trace-element collection, TPN and dialysis documentation, trend communication with dietitians, selenosis teaching, and symptom monitoring — not treating laboratory numbers without clinical context.
Before the TestDocumentation
Documentation must link selenium results to TPN route, supplements, collection timing, and symptom trends.
“Selenium drawn 08:15 royal blue metal-free tube; 58-year-old on long-term home TPN × 14 months with fatigue × 6 weeks. Result 32 mcg/L (adult ref 110–165); prior 48 mcg/L six months ago. Dietitian Martinez notified; TPN selenium content review ordered. Patient reports increased weakness climbing stairs; no garlic breath or nail changes.”
- TPN route, formula, and selenium additive content
- Supplement list, dose, and last administration time
- Collection timing, contrast history, and tube type
- Selenium value with laboratory reference interval and prior trend
- Fatigue, myopathy, hair/nail, and cardiac symptom assessment
- Prescriber/dietitian notification and replacement plan
Patient and Family Education
Use plain language: the blood test shows whether the body has enough selenium for important enzymes and helps the team adjust TPN or supplements safely.
Selenium NCLEX practice questions
Practice NCLEX-style clinical judgment focused on Selenium safety and nursing judgment. Use the case tabs (orders, results, assessment, nursing notes), then answer eight Next Gen–style items (including an ordered workflow step) and evaluate outcomes with the answer key.
Select a tab to view orders, results, assessment, and nursing note details for this case.
- Order: Selenium, serum; TSH; iron studies — long-term TPN monitoring panel
- Indication: 58-year-old on long-term home TPN with six weeks of increasing fatigue
- Timing: Selenium drawn today; prior selenium 48 mcg/L six months ago
- Related orders: TPN formula review; selenium supplementation adjustment per dietitian; repeat selenium in 8–12 weeks
- Result: Selenium 32 mcg/L (adult reference 110–165 mcg/L per Mayo); markedly below deficiency threshold
- Trend / prior value: Selenium declined from 48 to 32 mcg/L over six months; fatigue worsening
- Pending tests: TSH and iron results pending; dietitian TPN review scheduled
- Vital signs: T 36.8°C, HR 86/min, BP 118/72 mmHg, RR 16/min, SpO₂ 98% room air
- Symptoms: Fatigue, mild proximal leg weakness, no hair loss or garlic breath
- Focused assessment: Alert; reports difficulty climbing stairs; muscle strength 4/5 bilateral thighs; no edema
- Preparation notes: Royal blue metal-free tube; no contrast in past 96 hours; home TPN cycled nightly
- Collection events: Serum sent trace-elements routine; TPN additive list copied to chart
- Teaching gaps / safety concerns: Falling selenium on long-term TPN with new weakness — formula selenium content unverified
Answer key & rationale
Frequently Asked Questions
FAQ
Why is selenium monitored on long-term TPN?
NIH ODS notes selenium deficiency can occur with prolonged TPN without adequate supplementation. Mayo lists monitoring selenium replacement therapy as a primary indication with TPN targets above 70 mcg/L.
What tube is used for selenium testing?
the reporting laboratory specifies royal blue-top trace-element tube, metal-free, with 0.8 mL serum minimum. Standard tubes may contaminate trace-metal results.
What selenium level suggests deficiency?
Mayo cites deficiency usually below 40 mcg/L in adults with reference 110–165 mcg/L. NIH ODS notes ≥8 mcg/dL (80 mcg/L) is usually sufficient for enzyme activity — always use the reporting laboratory interval.
When should selenium collection be delayed?
Mayo recommends waiting at least 96 hours after gadolinium, iodine, or barium contrast before trace-element collection to avoid invalid results.
What is selenosis?
NIH ODS describes selenosis from chronic intake above the adult upper limit of 400 mcg/day with hair loss, nail brittleness, garlic breath, and gastrointestinal upset.
Are hemodialysis patients at risk for low selenium?
Yes. NIH ODS notes hemodialysis patients are at increased risk for deficiency — monitoring and replacement follow prescriber and dietitian protocol.
What is the adult RDA for selenium?
NIH ODS and the Institute of Medicine Dietary Reference Intakes cite 55 mcg/day for adults — distinct from serum monitoring thresholds used in TPN management.
References
References
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National Institutes of Health Office of Dietary Supplements. Selenium — Health Professional Fact Sheet. U.S. Department of Health and Human Services.https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
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Mayo Clinic Laboratories. Selenium, Serum (SES). Test Catalog.https://www.mayocliniclabs.com/test-catalog/overview/8653
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Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academies Press.https://nap.nationalacademies.org/catalog/10026/dietary-reference-intakes-for-vitamin-c-vitamin-e-selenium-and-carotenoids
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U.S. National Library of Medicine. Selenium Blood Test. MedlinePlus.https://medlineplus.gov/lab-tests/selenium-blood-test/
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Burk RF, Levander OA. Selenium. In: Ross AC, Caballero B, Cousins RJ, et al., editors. Modern Nutrition in Health and Disease. 11th ed. Lippincott Williams & Wilkins.https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/8653
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Rayman MP. Selenium and human health. Lancet. 2012;379(9822):1256-1268.https://pubmed.ncbi.nlm.nih.gov/22381456/
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Forceville X. Selénium: un oligo-élément essentiel en réanimation nutritionnelle. Nutrition Clinique et Métabolisme. 2020.https://www.sciencedirect.com/science/article/pii/S0989476520300065
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Mayo Clinic Laboratories. Trace Element Specimen Collection and Transport.https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/8653
Editorial Standards & Medical Review
About the author: Sid A. Abdala Balal, RN, writes evidence-based nursing education focused on diagnostic safety, clinical interpretation, and bedside nursing judgment.
Medical review: This guide is reviewed by Dr. Adam Sayedi, MD, for clinical accuracy, diagnostic safety, and alignment with current standards for Selenium.
Policies: Medical Review Process · Editorial Policy · Correction Policy