Iron is an abundant element required by all living organisms. In humans, it gives blood its characteristic red color and helps protect against bacterial infections. Low iron levels are especially common in women of child-bearing age and some children. They can cause iron deficiency anemia, which makes patients feel weak, tired and dizzy and may contribute to depression or irritability. Iron overdose occurs in some cases of excessive supplementation or in diseases that keep patients from processing this mineral properly. In severe cases, it can lead to organ damage and even death.

Doctors usually recommend serum iron tests for their patients when they suspect anemia or iron poisoning. This test measures the overall blood iron level, but not the person's rate of absorption or iron storage. Because of this, it may be useful to combine a serum iron test with a TIBC test, ferritin test or hemoglobin test. In general, men should have blood serum iron levels of about 50 to 150 micrograms per deciliter. Since women tend to have lower overall iron, they are considered normal if they get results of 35 to 145 mcg/dL. 

A blood iron test that produces results of greater than 150 mcg/dL, especially with a saturation rate of more than 60 percent, often indicates an iron overload in the blood. Below 35 to 50 mcg/dL could indicate anemia. People who have abnormal test results can often improve their iron levels by adjusting their diet, but should make sure that the test results don't indicate something more serious.