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Selenium deficiency

Symptoms, at-risk groups, and clinical context for selenium deficiency. Sourced from NIH Office of Dietary Supplements and StatPearls.

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Selenium deficiency in the US is uncommon because soil selenium content is generally adequate. The classic deficiency disease, Keshan disease (a cardiomyopathy), occurred in regions of China with severely selenium-deficient soils. Significant selenium deficiency in the US is mostly seen in people with severe malabsorption, on long-term parenteral nutrition, or with HIV.

Common symptoms

  • Cardiomyopathy — heart muscle weakening, heart failure (Keshan disease, severe deficiency)
  • Muscle pain, weakness, or wasting
  • Hair loss or thinning
  • Brittle nails, white nail beds
  • Fatigue
  • Compromised immunity, frequent infections
  • In children: Kashin-Beck disease (osteoarthropathy with joint deformities)
  • Possible association with hypothyroidism (selenium needed for thyroid hormone activation)
  • Macrocytic anemia (rare)

At-risk groups

  • People living in regions with severely selenium-poor soils (parts of China, New Zealand historically)
  • People with HIV, especially advanced disease
  • People on long-term total parenteral nutrition (TPN) without selenium
  • People with severe GI conditions affecting absorption (Crohn's, ulcerative colitis, short-bowel syndrome)
  • People on hemodialysis
  • People with severely restricted diets
  • Note: Brazil nuts contain extremely high selenium (~50-100+ µg per nut) — just 1-2 daily can exceed needs; supplementation is rarely necessary
When to see a doctor: Persistent fatigue with hair loss, brittle nails, or unexplained heart issues — especially in someone with malabsorption or HIV — warrants serum selenium or glutathione peroxidase testing. CAUTION: selenium has a relatively narrow safety margin. Toxicity (selenosis) at intakes >400 µg/day causes hair loss, brittle nails, garlic breath, and neurological symptoms. Don't supplement above the UL without medical guidance.
Sources: NIH ODS — Selenium Health Professional Fact Sheet · Selenium Deficiency — StatPearls (NBK482260)
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