A ferritin test measures the amount of ferritin in your blood. Ferritin is a blood cell protein that contains iron. A ferritin test helps your doctor understand how much iron your body is storing.
If a ferritin test reveals that your blood ferritin level is lower than normal, it indicates your body's iron stores are low and you have iron deficiency.
If a ferritin test shows higher than normal levels, it could indicate that you have a condition that causes your body to store too much iron. It could also point to liver disease, rheumatoid arthritis, other inflammatory conditions or hyperthyroidism. Some types of cancer also may cause your blood ferritin level to be high.