Iron (Fe) Unit Converter

Convert serum iron between µg/dL, µg/L, mg/L and µmol/L, with adult reference intervals for men and women.

Last updated 31 Aug 2026

Iron (Fe) converter

Mass ⇄ molar

Serum iron

Serum iron swings by 30% or more through the day — sample in the morning.

Reference groupRanges are laboratory-specific; confirm against your own report.

17.01µmol/LExample

Serum iron 95 µg/dL

Formula and conversion factor

µmol/L = µg/dL × 0.1791
µg/dL = µmol/L ÷ 0.1791

0.1791: derived from the atomic weight of iron, 55.845 g/mol
µg/L: µg/dL × 10
mg/L: µg/dL ÷ 100

Worked example

Serum iron 95 µg/dL
95 × 0.1791 = 17.01 µmol/L
95 µg/dL = 950 µg/L = 0.95 mg/L

Reference ranges

Serum iron has a marked diurnal rhythm, peaking in the morning and falling by up to 30% through the day. It is never interpreted alone.
Group	µg/dL	µmol/L
Men, adult	65 – 175	11.6 – 31.3
Women, adult	50 – 170	9.0 – 30.4
Children	50 – 120	9.0 – 21.5

What serum iron measures

Serum iron measures the iron bound to transferrin in circulation at the moment of sampling. That is a very small fraction of total body iron — around 3 mg against 3 to 4 g stored — and it turns over several times a day, which is why the number moves so much.

The diurnal swing is the practical problem. Levels peak in the morning and can fall by a third by evening, and a single iron tablet taken hours earlier can push a deficient patient into the normal range. Recent transfusion, acute inflammation and even a large meal all shift it. For these reasons serum iron on its own answers almost no clinical question.

Its value is entirely as a numerator. Divided by total iron binding capacity it gives transferrin saturation, which is a genuinely useful measure of iron supply to the marrow and one of the two tests — with ferritin — that define iron status. Order it as part of an iron panel, sample fasting in the morning, and interpret the saturation rather than the raw iron.

Frequently asked questions

How do I convert serum iron to µmol/L?

Multiply the µg/dL value by 0.1791. The factor comes from the atomic weight of iron, 55.845 g/mol. To go the other way, divide the µmol/L value by 0.1791 — or multiply by 5.585.

Why is my serum iron normal when I am iron deficient?

Serum iron fluctuates enormously through the day and rises after any iron-containing food or supplement. A normal value never excludes iron deficiency. Ferritin and transferrin saturation are the tests that answer the question.

Should I fast before an iron test?

Yes where possible. Sample in the morning after an overnight fast and before the day’s iron supplement, since a dose taken even the previous evening can raise the result substantially.

What does a high serum iron mean?

Most often recent supplementation or a haemolysed sample. Genuine elevation with a transferrin saturation above 45% suggests iron overload and warrants ferritin and, if persistent, HFE genotyping.

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References

Camaschella C. Iron deficiency. Blood. 2019;133(1):30–39.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, iron and iron-binding capacity.
IUPAC. Atomic weights of the elements, iron 55.845 g/mol.