Serum iron measures the amount of iron circulating in the blood and bound to the carrier protein transferrin. It is ordered with ferritin and a binding measurement to help assess iron status. It does not confirm or rule out a condition on its own, and the range printed on your report applies.
Iron is not free in the blood. It is carried by transferrin, and serum iron measures what is loaded onto that carrier at the moment of the draw.
What the test measures
Iron is absorbed from the gut, transported in the blood bound to transferrin, and stored in cells as ferritin. Serum iron measures the amount currently bound to transferrin. It moves through the day and responds to recent intake, so it describes a moment rather than a store.
Most iron study reports also print total iron-binding capacity, or TIBC, which estimates how much transferrin is available to carry iron, and transferrin saturation, a calculated value based on the two. Together they show how much of the carrying capacity is in use, which is a different question from how much iron is stored.
Serum iron is measured by colorimetric methods on serum or plasma, and different methods and analysers can produce different values.
Why it may be ordered
- As part of an iron studies panel, with ferritin and a binding measurement.
- When anaemia is being assessed and the clinician wants to see how iron is being carried.
- When iron overload is a question a clinician wants to explore.
- When inflammation is present, because serum iron falls as part of the acute-phase response.
- To follow a known value over time, where a clinician has chosen to do so.
It is not a universal screening test, and serum iron on its own is one of the weaker iron measurements. It is read with the other iron studies, the blood count, and the history.
The unit on your report
| What you may see | What it means |
|---|---|
| Serum iron, iron, Fe | The test name. Laboratories abbreviate it differently. |
| ug/dL | Micrograms per decilitre, a mass unit common on reports in India and the United States. |
| umol/L | Micromoles per litre, a molar unit common on reports in the United Kingdom and parts of Europe. |
| TIBC | Total iron-binding capacity, a measure of how much iron the carrier proteins could hold. |
| Transferrin saturation | A calculated percentage based on serum iron and the binding capacity. |
| Ferritin | A different test, and the usual marker of stored iron. |
Why this page does not print a range
Serum iron ranges differ by laboratory and method, and they can depend on age and sex. Some laboratories print a range built from their own population, and some adjust the interval for the analyser in use. Because the value moves through the day, a range cannot capture every fluctuation either, and the clinical context still affects how a value is read.
The range printed on the report that produced your value is the one that applies. Doctano keeps that printed range with the result and does not replace it with a general range. When a report prints a value for transferrin saturation, Doctano keeps the range printed beside that calculated line as well.
What a high value can mean
A higher serum iron means more iron is loaded onto transferrin at the time of the draw. It can be associated with increased iron stores or increased iron loading, and it can follow recent intake of iron. Haemolysis and liver injury can also raise the value, because they release iron into the blood.
A high serum iron is not a diagnosis, and it does not by itself show that iron is overloaded. It is read with ferritin, the binding capacity, transferrin saturation, and the history. A value inside the printed range does not exclude a problem either.
What a low value can mean
A lower serum iron means less iron is loaded onto transferrin. It can be associated with iron deficiency, and it also falls with inflammation, because the body sequesters iron as part of the acute-phase response. Blood loss and pregnancy can lower it too.
Because inflammation can lower serum iron without depleting stores, a low value is not the same as iron deficiency. It is read with ferritin, CRP where measured, the blood count, and the history, and the pattern across the iron studies matters more than one line.
What can move the value
- Time of day. Serum iron has a daily rhythm and is usually higher in the morning than later in the day.
- Recent iron intake. Iron taken shortly before the sample can raise the value for a period.
- Inflammation. The acute-phase response lowers serum iron independently of stores.
- Menstruation and pregnancy. Blood loss and increased demand change iron handling.
- Haemolysis. Red cells breaking in the sample release iron and raise the value.
- Collection materials. Contamination from collection tubes or equipment can affect some methods.
- Assay method. Different analysers can give different values on the same sample.
What to compare it with
Read serum iron with ferritin first, then with TIBC and transferrin saturation. Ferritin describes the stores, serum iron describes what is in transit, and the saturation describes how much of the carrying capacity is in use. CRP adds context when inflammation is present, and the blood count shows whether red cell formation has been affected.
The most useful comparison is the previous iron studies from the same laboratory, ideally collected at a similar time of day. Comparing a morning sample with an afternoon one can produce a difference that has nothing to do with iron status.
How to see the trend
Doctano reads the serum iron value, its unit, and the reference range printed on the report. It keeps the range with the result, normalizes the marker name across laboratories, and places the value on the profile's timeline. Each point still opens the report it came from, so the original page can be checked.
When reports use different units, Doctano normalizes them for the timeline so the points line up. Verify the value, the unit, and the collection time against the original report before treating a change as real.
What this page is not
This page explains the test in general. It does not interpret your result, diagnose a condition, or recommend treatment. It is not medical advice. Verify the value and the unit against the original report, and discuss the result with a qualified professional.