EmpeiriaIron, serum
Also known as
Fe, serum iron
Fe³⁺ inorganic ion
What this substance is
- formula
- Fe³⁺
- mass
- 55.845 g/mol
- monoisotopic
- 55.93329
- charge
- 3
- nucleus
- 26 protons, 30 neutrons (56Fe)
- electrons
- 23: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵
- InChIKey
- VTLYFUHAOXGGBS-UHFFFAOYSA-N
- ChEBI
- CHEBI:29034
Drawn from ChEBI's own curated 2D drawing, accepted only after its InChIKey, formula and charge matched the ChEBI release. Nothing here is hand-entered. Two masses are given because they answer different questions: the average is natural-abundance weighted and drives unit conversion; the monoisotopic value uses only the commonest isotope of each element and is what mass spectrometry measures.
3D model · Iron, serum
A schematic atom: a nucleus of 26 protons and 30 neutrons (the most common isotope, 56Fe), inside its electron shells, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵. The configuration matches the NIST Atomic Spectra Database ground state of Fe IV (6S<5/2>). The cloud is drawn as nested spheres because that term is an S state: the electron density really is spherical. Not to scale: shells are spaced on a square-root scale so the inner ones stay visible, and the nucleus is magnified about ten-thousand-fold.
Reference ranges
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This open edition shows a range only where a public-domain or openly licensed source states one, and none does for this marker yet. Compare your result with the range printed on your own lab report.
How it is measured
In practice
A health worker takes a small blood sample from a vein in your arm with a small needle. It usually takes less than five minutes. Your provider may ask you not to eat or drink for 12 hours first, and the test is usually done in the morning.
Serum iron is measured on a venous blood sample, usually ordered with transferrin, TIBC and ferritin as part of iron testing. A 12-hour fast may be requested and the sample is usually collected in the morning.
Before the test
- Fast (no food or drink) for 12 hours before the test if your provider asks.
- Have the test in the morning, as is usual for this test.
Where: laboratory
Source: Iron Tests -- MedlinePlus Medical Tests, U.S. National Library of Medicine cited · not yet checked by a person
In the lab
FerroZine colorimetric
In blood, iron rides on a carrier protein. The machine pulls the iron off, changes it into a form that reacts, and adds a dye that turns coloured when it meets iron. The stronger the colour, the more iron.
Fe3+ is released from transferrin by acid and detergent, reduced to Fe2+ by ascorbate, and complexed with FerroZine to form a coloured complex whose intensity is proportional to serum iron.
- Read by: Absorbance of the Fe2+-FerroZine complex
What can throw it off
- Haemolysis (iron released from red cells, falsely high)
- Iron supplements or metal-binding drugs (falsely low)
- IgM gammopathy (rare)
Sources: NHANES 2017-2018 Laboratory Procedure Manual, Iron (Refrigerated), CDC/NCHS; Non-anaemic iron deficiency. Aust Prescr 2021 (PMC8671013) cited · not yet checked by a person
What it reports on
-
liver
regulated by
The liver makes hepcidin, the hormone that plays a major role in keeping body iron in balance.
-
small intestine
transported by
Iron from the diet is absorbed in the small intestine, and hepcidin stops that absorption when iron is high.
Associated symptoms
Conditions this marker features in
-
high
Iron overload
· supportive
Serum iron is usually high (about 150–280 µg/dL in people without symptoms, versus 60–80 in healthy people). It is used to work out the transferrin saturation.
-
low
Anaemia caused by long-term illness
· supportive
Low serum iron (hypoferraemia) with normal or high ferritin is the typical iron pattern.
-
low
Low iron causing anaemia
· supportive
Often low, but blood iron varies through the day (it may be higher in the morning), so it is weak on its own.