Which of the following is a symptom of iron overdose?

Nausea is indeed a common symptom of iron overdose and is a direct result of the gastrointestinal irritation caused by excess iron in the body. When someone ingests a toxic level of iron, the unabsorbed portion can lead to various digestive issues, including nausea, vomiting, abdominal pain, and diarrhea. Understanding this symptom is vital, as it can help identify cases of iron toxicity early, allowing for prompt medical intervention.

In the context of the other choices, while rash, headache, and fatigue can occur due to a variety of causes, they are not specifically associated with iron overdose. For instance, a rash often indicates an allergic reaction or other dermatological issue, which is not typical in cases of iron toxicity. Headaches can result from numerous factors, including dehydration or tension, but again, are not specifically characteristic of iron overdose. Fatigue is commonly experienced due to various conditions, like anemia or general illness, but it does not serve as a key indicator of iron toxicity. Thus, nausea stands out as the notable symptom in this context, highlighting the need for awareness regarding the signs of iron overdose.