The normal total iron binding capacity is
**Core Concept**
The total iron binding capacity (TIBC) is a measure of all proteins available for binding mobile iron in the blood, including transferrin. It is an important indicator of iron status, reflecting both the amount of transferrin and the iron-binding capacity of transferrin.
**Why the Correct Answer is Right**
TIBC is elevated in iron deficiency anemia because the body produces more transferrin to increase iron absorption from the gut. Conversely, TIBC is decreased in iron overload conditions, such as hemochromatosis, due to the reduced production of transferrin. The normal range for TIBC is typically between 240-450 mg/dL.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because this value is below the normal range, which would indicate iron deficiency anemia.
**Option B:** Incorrect because this value is within the normal range, but it's not the specific value that is most commonly cited as the normal range for TIBC.
**Option C:** Incorrect because this value is above the normal range, which would indicate iron overload or other conditions affecting transferrin production.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that TIBC is not a direct measure of iron levels, but rather an indirect indicator of iron status through its reflection of transferrin levels.
**Correct Answer: B. 320 mg/dL**