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⚠ Patient from selenium-depleted region (parts of China, Eastern Europe) with unexplained cardiomyopathy — check selenium levels [3]
⚠ Long-term TPN without selenium — deficiency can develop within weeks to months [2]
⚠ Patient taking multiple supplements with selenium — check for cumulative intake exceeding 400 µg/day (selenosis risk) [4]
⚠ Hashimoto's thyroiditis patients — 200 µg/day may reduce anti-TPO antibodies, but exceed 400 µg/day and toxicity outweighs benefit [7]
⚠ Garlic breath + nail changes + hair loss in a supplement user — suspect selenosis [4]
🥗 Food first — build your daily 55 mcg
Check the foods you regularly eat — the bar fills toward your daily target.
Brazil nuts (1 nut, 5g)96 mcg
Yellowfin tuna (85g)92 mcg
Halibut (85g)47 mcg
Sardines (85g)45 mcg
Shrimp (85g)40 mcg
Beef steak (85g)33 mcg
Turkey (85g)31 mcg
Egg (1 large)15 mcg
Check your regular foods above
☑ Risk checker
Residence in selenium-depleted soil regions (parts of China, Scandinavia, Eastern Europe, NZ) [3]
Long-term total parenteral nutrition without selenium supplementation [2]
HIV/AIDS (increased oxidative stress and selenium utilization) [2]
Chronic kidney disease on hemodialysis (selenium loss) [2]
Inflammatory bowel disease (malabsorption) [2]
Post-bariatric surgery [2]
Phenylketonuria dietary restriction [1]
Select factors
🔬 Lab interpreter
Recommended test
Plasma/serum selenium
Plasma/serum selenium
Reference range / target
70–120 µg/L (optimal); <70 µg/L indicates deficiency
70–120 µg/L (optimal); <70 µg/L indicates deficiency
Reflects recent intake (days to weeks). Plasma selenoprotein P is a more functional marker but less widely available [3].
Full lab monitoring ↓⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
Selenium has one of the narrowest therapeutic windows of any essential nutrient — deficiency causes cardiomyopathy (Keshan disease) and impaired thyroid function, while excess (>400 µg/day) causes selenosis. 1–2 Brazil nuts/day is the simplest dietary strategy. Do not supplement in selenium-replete populations for cancer prevention (SELECT showed no benefit) [3] [4] [8].
1 Am I deficient?
Keshan disease regions (China, historical)40%
Eastern Europe (low-selenium soils)15%
New Zealand (pre-fortification)10%
Sub-Saharan Africa (variable)12%
Parenteral nutrition patients25%
General population (US, selenium-rich soils)1%
What happens as status declines
Subclinical deficiency
Plasma selenium 40–70 µg/L. Reduced glutathione peroxidase activity. Increased oxidative stress markers. No clinical symptoms yet [3].
Moderate deficiency
Impaired immune function. Thyroid dysfunction (impaired T4→T3 conversion). Myalgia and muscle weakness. Nail bed changes (whitening). Increased viral virulence (Coxsackievirus mutations — relevance to Keshan disease) [3].
Severe deficiency (Keshan disease)
Endemic cardiomyopathy: dilated cardiomyopathy, heart failure, arrhythmias. Occurs in regions with soil selenium <0.05 mg/kg. Predominantly affects children and women of childbearing age [3].
Kashin-Beck disease
Osteoarthropathy with cartilage necrosis and joint deformities affecting children in selenium + iodine-deficient regions. Multifactorial (mycotoxins may contribute). Found in a belt from Tibet through China to Siberia [3].
Risk factors
• Residence in selenium-depleted soil regions (parts of China, Scandinavia, Eastern Europe, NZ) [3]
• Long-term total parenteral nutrition without selenium supplementation [2]
• HIV/AIDS (increased oxidative stress and selenium utilization) [2]
• Chronic kidney disease on hemodialysis (selenium loss) [2]
• Inflammatory bowel disease (malabsorption) [2]
• Post-bariatric surgery [2]
• Phenylketonuria dietary restriction [1]
🧬 How Selenium works ▼
2 How much do I need?
👤 Adults: Specific dosage data under clinical review
👴 Elderly: Specific dosage data under clinical review
🤰 Pregnancy: Specific dosage data under clinical review
👦 Pediatric: See guidance
Infants 0–6 months: 15 µg/day AI; 7–12 months: 20 µg/day. Children 1–3 years: 20 µg/day; 4–8 years: 30 µg/day [1]. Keshan disease in children (endemic cardiomyopathy) was a devastating con
🏃 Athletes: Standard dose
⚖️ Obesity: Standard dose
Fat-soluble compounds may require dose adjustment in obesity.
🩺 Renal: Consult specialist
Dose adjustment may be needed in renal impairment.
🌱 Vegan: Standard dose
How to take
🍽 Timing: Can be taken at any time of day, with or without food. Organic selenium (selenomethionine) is absorbed better than inorganic forms [1].
💊 With food: No specific requirement. Selenium absorption from food and supplements is generally high (>50% for organic forms) [1].
3 Which form?
| Form | Bioavailability | Vegan | Cost |
|---|---|---|---|
| ['Selenomethionine', 'preferred', 'Organic form found in Brazil nuts, grains, and selenized yeast. Approximately 90% absorbed. Non-specifically incorporated into body proteins in place of methionine, creating a selenium reservoir [1].'] | Standard | Check label | |
| ['Sodium selenite', 'common', 'Inorganic form. Approximately 50% absorbed. Reduced to selenide before incorporation into selenoproteins. Does not accumulate in tissue protein reserves [1].'] | Standard | Check label | |
| ['Selenium-enriched yeast', '', 'Contains predominantly selenomethionine (~60–80%) plus other organic selenium species. Used in the SELECT and NPC trials. Absorption and retention similar to selenomethionine [5].'] | Standard | Check label | |
| ['Methylselenocysteine', '', 'Organic form found in garlic and cruciferous vegetables. Metabolized to methylselenol, which has distinct anticarcinogenic properties in preclinical models [2].'] | Standard | Check label |
4 Common questions
Can I just eat Brazil nuts instead of supplements? ▼
Yes — 1 to 2 Brazil nuts per day typically provides 70–180 µg selenium, meeting or exceeding the RDA [6]. However, selenium content varies enormously by growing region (10-fold range). Do not eat large quantities — consuming 5+ nuts daily regularly can lead to chronic selenosis [4]. Two nuts per day is a reasonable maximum.
Does selenium prevent cancer? ▼
The evidence is mixed. The NPC trial suggested benefit for prostate cancer, but the larger SELECT trial (n = 35,533) found no reduction in prostate or other cancers in a selenium-replete population [5] [8]. Current evidence does not support selenium supplementation for cancer prevention in people with adequate selenium status. The relationship appears U-shaped: both low and high levels may increase risk [4].
Is selenium important for thyroid health? ▼
Yes — the thyroid has the highest selenium concentration per gram of any organ. Selenoprotein deiodinases convert T4 to active T3 [7]. Several RCTs have shown that 200 µg/day selenium reduces anti-TPO antibodies in autoimmune thyroiditis, though the clinical significance for preventing hypothyroidism progression is still debated [7].
What does selenium toxicity look like? ▼
Chronic selenosis (>400 µg/day) causes a characteristic garlic-like breath odor, brittle hair and nails, nail loss, skin rash, gastrointestinal symptoms, and peripheral neuropathy [4]. Acute toxic ingestion can cause cardiac failure and death. The margin between optimal intake and toxicity is narrower than for most other essential minerals [4].
5 Clinical evidence
Strong
Prevention and treatment of Keshan disease (endemic cardiomyopathy in selenium-depleted regions of China) through supplementation [3]. Essential role in thyroid hormone metabolism: deiodinases convert T4 to active T3. Combined selenium + iodine deficiency causes myxedematous cretinism [7]. Antioxidant defense via glutathione peroxidase system [2]. HIGH
Moderate
Thyroid autoimmunity: selenium supplementation (200 µg/day) reduced anti-TPO antibodies in patients with autoimmune thyroiditis in several RCTs, though clinical outcomes (hypothyroidism prevention) are less clear [7]. Prostate cancer: the NPC trial (n = 1,312) showed 52% reduction in prostate cancer incidence with 200 µg/day selenized yeast, but this was a secondary endpoint and SELECT (n = 35,533) found no benefit [5] [8]. Male fertility: selenium is critical for spermatogenesis and sperm motility [2]. MODERATE
Insufficient
Cancer prevention in selenium-replete populations: the SELECT trial showed no reduction in prostate or other cancers and a non-significant trend toward increased type 2 diabetes [8]. Cardiovascular disease prevention: observational associations are U-shaped, suggesting harm at both low and high selenium levels [4]. HIV progression: some evidence for benefit in selenium-deficient populations, but insufficient for recommendation [2]. LOW
6 Safety, toxicity & adverse events
Absolute contraindications
✕ Selenosis (serum selenium >400 mcg/L) — garlic breath, hair loss, nail brittleness, neuropathy
Relative
⚠ Non-melanoma skin cancer history — SELECT trial showed increased risk with selenium supplementation in selenium-replete individuals
⚠ Type 2 diabetes risk — some evidence of increased T2D risk at high selenium status
🚩 Red flags
● Garlic-like breath + hair loss + nail changes in a supplement user — selenosis until proven otherwise [4]
● Unexplained dilated cardiomyopathy in a patient from a selenium-depleted region or on TPN — check selenium levels [3]
● Patient taking multiple supplements — total selenium from all sources may exceed 400 µg/day unknowingly [4]
● Thyroiditis patient on 200 µg selenium/day plus eating Brazil nuts — cumulative dose may be toxic [4]
● Peripheral neuropathy with no other explanation + supplement use — consider chronic selenosis [4]
7 Interactions
Drug interactions
Cisplatin Moderate
Mechanism: Selenium may reduce cisplatin-induced nephrotoxicity through antioxidant mechanisms. Theoretical concern that antioxidant supplementation could reduce chemotherapy efficacy, though clinical data are mixed. [2]
Effect: Possibly reduced nephrotoxicity. Uncertain impact on antitumor activity. [2]
Action: Discuss with oncologist before supplementing during chemotherapy. Do not supplement without medical guidance [2].
Statins (HMG-CoA reductase inhibitors) Minor
Mechanism: Some data suggest selenium supplementation may modestly alter lipid profiles. The HATS trial noted that antioxidants (including selenium) blunted the HDL benefit of niacin-simvastatin. [4]
Effect: Potentially reduced benefit of statin-niacin combination therapy. [4]
Action: Clinical significance uncertain. Avoid high-dose selenium supplements during statin-niacin combination therapy [4].
Anticoagulants (warfarin) Minor
Mechanism: At toxic doses, selenium may have antiplatelet activity. At nutritional doses, no significant interaction expected. [4]
Effect: Theoretical increased bleeding risk at excessive selenium intake. [4]
Action: Keep selenium within recommended intake range (55–200 µg/day) [4].
Barbiturates (phenobarbital) Minor
Mechanism: Selenium may enhance the sedative effects of barbiturates through unclear mechanisms (animal data). [2]
Effect: Increased sedation at high selenium doses (primarily animal data). [2]
Action: Clinical significance in humans uncertain. Maintain recommended selenium intake [2].
Supplement synergies
Vitamin E · 15 mg/day vitamin E (RDA)
Complementary antioxidant mechanisms: glutathione peroxidase (selenium-dependent) protects cell membranes alongside alpha-tocopherol [1].
Complementary antioxidant mechanisms: glutathione peroxidase (selenium-dependent) protects cell membranes alongside alpha-tocopherol [1].
Iodine · 150 µg/day iodine
Both are essential for thyroid function. Selenium-dependent deiodinases convert T4→T3. In combined deficiency, selenium supplementation alone can worsen hypothyroidism (must correct iodine first) [7].
Both are essential for thyroid function. Selenium-dependent deiodinases convert T4→T3. In combined deficiency, selenium supplementation alone can worsen hypothyroidism (must correct iodine first) [7].
Zinc · 11 mg/day (men), 8 mg/day (women)
Zinc and selenium both support immune function and antioxidant defense. Co-deficiency is common in populations with poor micronutrient intake [2].
Zinc and selenium both support immune function and antioxidant defense. Co-deficiency is common in populations with poor micronutrient intake [2].
8 Laboratory monitoring
Plasma/serum selenium Primary
Target: 70–120 µg/L (optimal); <70 µg/L indicates deficiency · If deficiency suspected or monitoring supplementation in high-risk groups [3].
Plasma selenoprotein P (SELENOP) Secondary
Target: Maximized at ~105 µg/day intake
Erythrocyte glutathione peroxidase (GPx) activity Secondary
Target: Activity plateaus at adequate selenium status
Thyroid function tests (TSH, free T4, free T3) Secondary
Target: Per standard thyroid reference ranges
9 Regulatory
United States (FDA): Classified as a dietary supplement. FDA-authorized qualified health claim: 'selenium may reduce the risk of certain cancers' (with caveats). UL: 400 µg/day [1].
European Union (EFSA): Authorized health claims for protection of cells from oxidative stress, normal thyroid function, immune function, spermatogenesis, hair and nail maintenance [9]. UL: 300 µg/day (EFSA, stricter than US) [4].
Japan (MHLW): Eligible for Foods with Function Claims. Recommended intake: 30 µg/day (adult males). Upper limit: 450 µg/day.
South Korea (MFDS): Registered health functional food ingredient. Approved claims: antioxidant activity and immune function.
10 US supplement products
1,868
on-market products containing Selenium (NIH DSLD)
Brands carrying Selenium (461)
Click a brand to see its Selenium products.
11 Frequently paired with
12 References (9)
[1]Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academies Press; 2000. doi:10.17226/9810 REVIEW Accessed: 2026-05-29
[2]National Institutes of Health, Office of Dietary Supplements. Selenium — Fact sheet for health professionals. Updated 2024. ods.od.nih.gov REVIEW Accessed: 2026-05-29
[3]Rayman MP. Selenium and human health. Lancet. 2012;379(9822):1256-1268. doi:10.1016/S0140-6736(11)61452-9 REVIEW Accessed: 2026-05-29
[4]Vinceti M, et al. Selenium for preventing cancer. Cochrane Database Syst Rev. 2018;1:CD005195. doi:10.1002/14651858.CD005195.pub4 REVIEW Accessed: 2026-05-29
[5]Clark LC, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. JAMA. 1996;276(24):1957-1963. doi:10.1001/jama.1996.03540240035027 REVIEW Accessed: 2026-05-29
[6]U.S. Department of Agriculture. FoodData Central. fdc.nal.usda.gov GOVERNMENT Accessed: 2026-05-29
[7]Winther KH, et al. Does selenium supplementation affect thyroid function? Results from a systematic review and meta-analysis. Thyroid. 2020;30(2):246-256. doi:10.1089/thy.2019.0575 META-ANALYSIS Accessed: 2026-05-29
[8]Lippman SM, et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009;301(1):39-51. doi:10.1001/jama.2008.864 RCT Accessed: 2026-05-29
[9]EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific opinion on the substantiation of health claims related to selenium. EFSA J. 2009;7(9):1220. doi:10.2903/j.efsa.2009.1220 GOVERNMENT Accessed: 2026-05-29
13 Related articles
Auto-populated from GMJ Newsroom. Articles tagged "Selenium".
14 Cite this page
Vancouver: Pkhakadze G. Selenium — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Jun 01]. Available from: https://supplement.ge/ingredients/selenium/
APA 7th: Pkhakadze, G. (2026). Selenium — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/selenium/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Institution: Public Health Institute of Georgia (PHIG)
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: December 2026
References: 9 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "Selenium — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/selenium/ CC BY 4.0.
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Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG