Copper deficiency is uncommon in healthy adults eating a typical diet because copper is widespread in food (organ meats, shellfish, nuts, seeds, dark chocolate). When deficiency occurs, the most common cause is excess zinc supplementation — chronic zinc intake above 40 mg/day blocks copper absorption. Other causes include bariatric surgery and rare genetic conditions.
Common symptoms
Anemia that doesn't respond to iron supplementation (often microcytic or sideroblastic)
Low white blood cell count (neutropenia) — increased infection risk
Numbness, tingling, or loss of sensation in hands and feet
People with Menkes disease (rare X-linked genetic disorder of copper transport)
Premature infants
People with chronic diarrhea or short-bowel syndrome
When to see a doctorUnexplained anemia that doesn't respond to iron, low white blood cell count, or progressive numbness in hands and feet warrants serum copper and ceruloplasmin testing. CRITICAL: if you take a high-dose zinc supplement long-term, you should know that 40+ mg/day of zinc can cause copper deficiency. Many cases are misdiagnosed because the connection isn't well known. The neurological damage may not fully reverse, so early recognition matters.