Serum iron
Amount of iron circulating in the blood, one building block of iron testing
Also known as
Definition
Serum iron shows how much iron is currently circulating in your blood. Your body needs iron mainly to make hemoglobin, which carries oxygen from the lungs to the rest of the body. The value varies throughout the day, is often higher in the morning and depends on when you last took in iron. That is why it is usually assessed together with ferritin, transferrin and total iron-binding capacity.
| Parameter | Value |
|---|---|
| Unit | µg/dl (µmol/l) |
| Reference Range | Typical for adults: men 59–158 µg/dl (10.6–28.3 µmol/l), women 37–145 µg/dl (6.6–25.9 µmol/l). Laboratories vary; the reference range on your own report is what counts, and your doctor interprets it. |
Agree on your personal target range with your doctor.
Conversion: 1 µg/dl equals about 0.179 µmol/l.
↓ What a low value means
A low value can be linked to iron deficiency, for example from heavy menstrual bleeding, long-term bleeding in the digestive tract, poor iron absorption in the gut or too little iron in the diet. It can also be lower during pregnancy and during menstruation. Iron deficiency is the most common cause of anemia, but not every low value means anemia. Discuss abnormal results with your doctor.
↑ What a high value means
A high value can be linked to iron overload (hemochromatosis), accelerated breakdown of red blood cells (hemolytic anemia), liver disease such as hepatitis, frequent blood transfusions, iron poisoning or lead poisoning. Medicines such as birth control pills or estrogens can also change iron levels. A single abnormal value does not automatically mean a condition that needs treatment.
When to test
Serum iron is measured with signs of too little or too much iron, with anemia related to chronic disease, and for follow-up. Blood is usually drawn in the morning while fasting, sometimes after a 12-hour fast. Mention your medicines, such as antibiotics, birth control pills, blood pressure, cholesterol or gout medicines and testosterone, but do not stop anything without talking to your doctor.
Frequently asked questions
Why is serum iron alone not enough? +
The value varies throughout the day and depends on when you last took in iron. Ferritin says more about iron stores. That is why several iron markers are often measured together, such as ferritin, transferrin and total iron-binding capacity.
What is the difference between serum iron and ferritin? +
Serum iron measures the iron currently circulating in the blood. Ferritin shows how much iron is stored in the body. The two values complement each other when assessing iron status.
Why do I need to fast for the test? +
Because the serum iron value changes depending on your most recent iron intake. The test is often done in the morning after a fasting period, sometimes 12 hours. Your practice or laboratory gives the exact instructions.
Which medicines can affect the value? +
Among others, antibiotics, birth control pills and estrogens, blood pressure and cholesterol medicines, gout medicines, testosterone and deferoxamine. Never stop a medicine on your own; talk to your doctor first.
Serum iron
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.