Excess zinc is toxic. Too much zinc will interfere with the metabolism of other minerals in the body, particularly iron and copper. Symptoms of zinc toxicity occur after ingestion of 2gm of zinc or more.
Zinc toxicity, along with an induced copper deficiency, is becoming more of a problem as the routine and chronic use of large doses of zinc becomes more common. Those on long-term supplementation should be monitored for zinc and copper status.
One 17 year old male was found to have fatigue, hypocupremia, anemia, leukopenia, and neutropenia after 6 – 7 months using large daily doses of zinc for acne.