Acute toxicity - iron poisoning can be caused by taking too many iron suppliments at once. It is expecially dangerous for children taking mom's iron suppliments, ingesting too much at once for such a small system.
Acute iron poisoning can cause damage intestinal lining, change body pH, cause shock and liver failure.
Iron overload / chronic iron poisoning can occur from cosuming too much iron but it is most common in people with hemochromatosis, a hereditary condition which causes a person to absorb too much iron. The excess iron in their system can cause the skin to darken, weight loss, fatigue, weakness and abdominal pain. If not stopped it can cause heart and liver damage, cancer, diabetes or other conditions. Hemochromatosis is managed simply by removing blood from the sufferer.