BiomarkersSerum iron

Blood & iron

Serum iron

Iron circulating in your blood right now

On your report it may say: Iron, Fe

Serum iron measures iron moving through the blood at the moment of the test. It swings through the day and after meals, so it's read together with ferritin, TIBC and transferrin saturation.

Updated 2026-10-26

Typical ranges · µg/dL

Low below 60
In range 60–170
High 170+

µmol/L = µg/dL × 0.179

A single serum iron result isn't enough to diagnose deficiency or overload.

Ranges vary by lab, age and sex. The range printed on your report applies.

If it's low

Less iron is circulating, which may reflect low stores or inflammation.

Common causes

  • Low iron stores
  • Inflammation
  • Blood loss
  • Afternoon or evening testing

What you might notice

  • Same as low ferritin: tiredness, breathlessness

If it's high

High serum iron can follow a recent iron dose or meal, or suggest iron overload.

Common causes

  • Iron taken shortly before the test
  • Iron overload conditions
  • Liver damage

What you might notice

  • Usually none

Testing

Who should test
As part of an iron panel when ferritin or hemoglobin is abnormal.
How to prepare
Morning, fasting test; skip iron supplements for 24 hours before.
When to retest
With your iron panel, 8–12 weeks after a change.

What can help

Food sources

See ferritin

See a doctor if the panel suggests overload or very low iron.

Common questions

Why fasting?

Food and supplements raise iron for several hours.

Which iron test matters most?

Ferritin is the most useful single test for stores.

Explore further

Sources

  1. MedlinePlus (US National Library of Medicine): Iron tests
  2. NIH Office of Dietary Supplements: Iron fact sheet for health professionals

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For general education only, not medical advice. Ranges shown are typical for adults; the range printed on your lab report applies. Talk to a qualified doctor about your results.