What does a ferritin test measure?

Ferritin is a protein that stores iron, and measuring it gives a picture of how much iron your body has in reserve rather than how much is circulating right now. That is why it is often ordered alongside other iron measurements rather than alone.

A low result generally points toward depleted stores. A high one is less straightforward, because ferritin also rises with inflammation, infection and liver conditions, which means a normal or high ferritin does not always rule out an iron problem.

That ambiguity is the reason interpretation belongs with a clinician who knows whether anything else is going on. Reference ranges also vary between laboratories, so a result close to a boundary is a conversation rather than a conclusion.