What it measures
Serum iron is the amount of iron circulating in the blood at the time of the sample, mostly carried on transferrin. It changes through the day and after meals, so it is usually read with ferritin, TIBC and transferrin saturation rather than on its own.
Why people test it
- Part of iron studies, used with ferritin to look into tiredness or anaemia.
- Checked when iron overload, such as haemochromatosis, is suspected.
- Used to monitor iron tablets or infusions.
- Endurance athletes often have iron studies alongside ferritin, as heavy training can lower iron levels.
Typical range
Ranges vary between labs with the method used, age and sex, and your report shows the lab's own range. One NHS trust's lab uses 9.0 to 30.4 µmol/L for women and 11.6 to 31.3 µmol/L for men. Source: Leeds Teaching Hospitals NHS Trust: Blood Sciences Reference Range Database v3.20.
Finger-prick or vein?
A finger-prick sample is usually fine. Red blood cells contain iron, so a sample that breaks down (haemolyses) can read falsely high.
Serum iron is higher in the morning and rises after iron-rich meals or supplements, so some labs ask for a morning, fasting sample.
