Feeling tired all the time? This test checks your body's true iron reserves. The Ferritin Serum test doesn't just measure the iron floating in your blood; it measures the storage protein that holds your body's iron supply. This makes it the single most reliable test for detecting iron-deficiency anemia, often before your other blood counts even drop. It's also used to diagnose iron overload (hemochromatosis). This is the definitive test to find out if low iron stores are the root cause of your fatigue. Stop guessing and get the real answer.