This test is conducted to diagnose iron deficiency in your body or if there is more than required iron in your blood.
The mineral iron is part of hemoglobin, a protein that carries oxygen from our lungs throughout our body.This oxygen is then stored in our muscles to use for different bodily functions. If there is iron deficiency it leads to anemia. There is less oxygen in our body.
On the converse side, too much iron can cause iron poisoning. Hence, in both the cases, you may be required to get an iron test.