However, iron can build up to toxic levels gradually within the body, especially in older men. Early signs that you may have too much iron in your system are abdominal pain, severe nausea, diarrhea, or vomiting with blood. As iron toxicity intensifies, you may begin to feel weak or even collapse. Your skin may look pale, while your lips, hands, and fingernails begin to take on a bluish tinge. Shallow breathing and a weak, rapid heartbeat are also among the later warning signs of iron overdose.
Extreme toxicity can cause convulsions and coma.
When first taking an iron supplement, you may find your stools turning black or gray. This is not a problem. However, if you notice blood in the stool, seek treatment immediately. Emergency treatment is also essential if you have chest pain, chills, hives, shortness of breath or a skin rash or if you lose consciousness. If you develop these symptoms, discontinue taking the supplement and call your doctor.