A ferritin test determines the blood level of ferritin, which is  an iron-containing blood protein.

If a ferritin test shows that your blood ferritin level is lower than normal, it means that your body’s iron stores are depleted and you have iron deficiency. As a result, you may be anemic.

If your ferritin levels are higher than normal, you may have a condition that causes your body to store too much iron. It could also indicate liver disease, rheumatoid arthritis, other inflammatory disorders, or hyperthyroidism. Some cancers can also cause an increase in blood ferritin levels.