Iron

The iron test measures the amount of iron in blood at the time of sampling, bound to transferrin, the protein that carries it to bone marrow and other tissues. It is most often performed to investigate iron deficiency or the cause of anaemia, and less often for suspected iron excess. Iron levels change during the day, after meals and with inflammation, so results are interpreted alongside ferritin, UIBC, TIBC and a blood count.

Who the test is for

• people whose blood count shows anaemia or small red blood cells (low MCV);
• people with persistent fatigue, pallor, breathlessness on exertion or increased hair loss, together with ferritin;
• women with heavy periods and pregnant women;
• people following a vegan diet, with coeliac disease or after stomach or bowel surgery;
• people with suspected iron excess, for example with high ferritin or a family history of haemochromatosis;
• people taking iron replacement, when a doctor decides treatment needs monitoring.

What serum iron indicates

Most iron in the body is found in haemoglobin within red blood cells, which carries oxygen. Some is stored in the liver, spleen and bone marrow, while only a small amount travels through the blood at any time. Serum iron measures precisely this circulating portion.

Serum iron alone therefore poorly reflects iron stores. It can be low in inflammation despite adequate stores, and normal early in deficiency. Stores are best reflected by ferritin, while UIBC and TIBC show the amount of transferrin in blood and how many binding sites remain free. A doctor calculates transferrin saturation from iron and TIBC; it is not printed on the report and indicates how much iron is available for blood formation.

Save with a panel

Test Iron is also included in these panels.

Iron panelCBC, iron, UIBC TIBC, ferritin30.00€Details ›Healthy hair, skin and nails panelVitamin B12, zinc, Vitamin D, folic acid, iron and 3Price of individual tests: 145.80€121.00€Details ›Energy balance panelvitamin D, vitamin B12, folic acid, calcium, magnesium and 498.50€Details ›

All panels including Iron (13) ›

Preparation and sample

Iron is measured in venous blood. Come in the morning after fasting, because iron is usually higher in the morning and also rises after meals. You may drink water. Do not take iron tablets, drops or syrup, or iron-containing multivitamins, for 24 hours before sampling unless your doctor advises otherwise.

Tell your doctor about a recent iron infusion or blood transfusion, infection or pregnancy, because all these affect results.

How results are interpreted

Iron is expressed in µmol/L. The reference interval depends on sex, age and method and is printed on your report. Iron varies from day to day even in healthy people, so one result outside the interval rarely gives an answer on its own. A doctor interprets it alongside ferritin, UIBC, TIBC, transferrin saturation, blood count and your symptoms.

Low iron

• Iron deficiency: with low ferritin, high UIBC and TIBC and low transferrin saturation. The most common causes are blood loss, for example through heavy periods or from the digestive tract, inadequate dietary iron, reduced absorption (coeliac disease, stomach surgery) and increased requirements during pregnancy and growth.
• Inflammation and chronic disease: in infection, rheumatic disease, chronic kidney disease or malignancy, the body retains iron in stores. Iron is then low, but ferritin is normal or elevated and UIBC and TIBC are normal or low.
• Blood sampling later in the day, when levels are naturally lower.

A doctor establishes the cause of deficiency because treatment depends on it. In men and postmenopausal women, iron deficiency often also requires digestive tract investigation to exclude hidden bleeding.

High iron

• most often an iron tablet or infusion before blood sampling;
• repeated blood transfusions and some anaemias in which red blood cells break down more rapidly or are produced ineffectively, such as more severe forms of thalassaemia;
• acute liver injury, for example in hepatitis, when iron is released from damaged cells;
• hereditary haemochromatosis, in which the body absorbs too much dietary iron over many years.

If iron remains high on repeat fasting testing, transferrin saturation is above approximately 45 % and ferritin is elevated, a doctor assesses whether further iron overload investigation is needed. If a child swallows iron tablets, seek emergency medical help immediately.

Examples of interpreting the complete report are explained in How to interpret serum iron results.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed on the Contact page). Prices for all tests and panels are available in the service price list. When investigating iron deficiency or excess, the Ferro (Iron) Panelis more practical, combining blood count, iron, UIBC, TIBC and ferritin from one blood sample.

Frequently asked questions

Do I need to fast for an iron test?

Yes. Come in the morning after fasting because meals and time of day affect blood iron. You may drink water, and should avoid iron preparations for 24 hours beforehand unless your doctor advises otherwise.

Is low iron the same as anaemia?

No. Anaemia means low haemoglobin and is visible in a blood count. Low iron may accompany iron-deficiency anaemia but also temporary inflammation, and iron deficiency can exist before anaemia develops. Read more in our article about iron-deficiency anaemia.

Should I take iron if my result is low?

Not on your own initiative. If inflammation is the cause, supplementation does not help, and the body cannot excrete excess iron by itself. A doctor first checks ferritin and the cause, then decides on replacement. We discuss tablet tolerability in our article on iron replacement and tablet side effects.

Why is iron low when ferritin is normal?

Most often because of inflammation or infection, when the body retains iron in stores, or because blood was taken later in the day. If stores are normal, this is not deficiency. With inflammation, ferritin can be normal even when stores are reduced, so a doctor also considers CRP and transferrin saturation.