Serum Iron
Serum iron measures the amount of iron actively circulating in your blood, most of it bound to a transport protein called transferrin. It's a snapshot of iron in transit, not your total stored iron.
Serum iron helps complete the picture of your iron status when read together with transferrin, TIBC, and transferrin saturation. Because it captures iron moving through your bloodstream, it supports understanding of how well iron is being delivered to where it's needed. On its own it's rarely conclusive, which is why it's almost always interpreted as part of a panel.
A high serum iron can reflect iron overload, recent iron supplements, or certain liver conditions, but it can also fluctuate for everyday reasons. Iron levels naturally vary through the day and can be raised by a recent iron-rich meal or supplement. A single elevated value usually needs context from the rest of the panel.
A low serum iron can suggest iron deficiency or that iron is being held back during inflammation. It's most informative when viewed alongside ferritin and transferrin saturation rather than alone.
Serum iron varies through the day and with recent meals, so timing and reference ranges matter. A clinician can interpret your value in the context of the full iron panel and advise on any next steps.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.
Associations to explore with a clinician, not a diagnosis from a single number.