Circulating iron Serum Iron
The iron travelling in your blood right at that moment.
Also printed asIron · Fe · Iron Level
What it measures
The iron travelling in your blood at the moment the sample was taken.
Swings with meals, supplements and the time of day, so it means little without ferritin and transferrin saturation beside it.
Why it matters for how long you stay well
It only earns its place read with binding capacity and stores; on its own it is the least reliable iron number on the panel.
How it shows up in daily life
It swings through the day and jumps after an iron tablet, so a single reading tells you very little.
High and low readings
When it reads high
Often a supplement taken that morning; overload is the rarer cause.
When it reads low
Low circulating iron; ferritin tells the fuller story.
What moves it
Daily life
- what you ate that morning
- the time of day of the draw
- inflammation, which hides iron away
- iron in your diet
Medicines known to shift it
- iron supplements (raise it)
Listed so a result can be read in context. It is not advice to start, stop or change any medicine; that decision belongs with your physician.
Read it with
Markers that move this one, or that this one moves. One number read alone can mislead.
- Transferrin saturationKnown mechanism
As this rises, Transferrin saturation is calculated from it
Saturation is your circulating iron divided by your binding capacity. It is arithmetic on two results you already have, not another test on your blood.
- hs-CRP, the inflammation dialKnown mechanism
hs-CRP pulls it down
During an infection your body hides iron away from the bloodstream, partly to keep it from feeding bacteria. So circulating iron drops while you are unwell.
Common questions
What does Serum Iron measure?
The iron travelling in your blood at the moment the sample was taken. Swings with meals, supplements and the time of day, so it means little without ferritin and transferrin saturation beside it.
What does a high Circulating iron result usually mean?
Often a supplement taken that morning; overload is the rarer cause.
What does a low Circulating iron result usually mean?
Low circulating iron; ferritin tells the fuller story.
What is the usual reference range for Circulating iron?
A broad adult reference band is 60–170 µg/dL. For women the band is 50–170 µg/dL. Labs differ, so read your result against the band printed on your own report.
Educational only, not a diagnosis. A single number means little without your history and the rest of your panel, so discuss your own results with your physician.
Typical adult reference band
- Men
- 60–170 µg/dL
- Women
- 50–170 µg/dL
Labs differ. The band printed on your own report is the one that applies to your result.
Reported in µg/dL
Ageing relevance
2/5
Relevant to the ageing of one organ, or to disease screening.
Worth knowing
It rises and falls through the day, so the same person can test low in the evening and normal in the morning.
Have a report with this marker on it? Read it in context.
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