Iron · Blood

Transferrin saturation

The percentage of the transport protein transferrin that is loaded with iron; the most important sign of iron overload.

At a glance

Measured in blood
In 7 test panels
Check the preparation

Explanation

Transferrin saturation: what is measured?

Transferrin is the protein that carries iron through the blood; each molecule can bind two iron atoms. The transferrin saturation (also called iron saturation) is a calculated value: the serum iron divided by the total iron binding capacity (TIBC, all binding sites on transferrin), expressed as a percentage. In iron deficiency the percentage is low, because there is little iron and the body makes extra transferrin; in iron overload it is high, because the transferrin is full.

What can it detect?

Iron overload, including hereditary hemochromatosis (saturation above 45 percent, together with a raised ferritin)
Iron deficiency and iron deficiency anemia (low saturation, together with a low ferritin)
Distinguishing between iron deficiency and anemia due to a chronic disease

Result

What does the result mean?

Transferrin saturation too high

According to the Dutch guideline on hemochromatosis, a transferrin saturation above 45 percent is the threshold above which iron overload should be considered, especially if the ferritin is also raised. That combination may point to hereditary hemochromatosis, a condition in which the body absorbs too much iron from food and stores it in the liver, joints, pancreas and heart. A single raised value, however, is often harmless: iron tablets or an iron-rich meal shortly before the blood draw, the morning peak of serum iron, alcohol use or liver damage temporarily raise the percentage. Symptoms of iron overload usually only appear after the age of forty: tiredness, joint pain, abdominal pain, a darker skin, diabetes and, in men, erection problems.

Transferrin saturation too low

A low transferrin saturation fits iron deficiency: there is little iron and a lot of empty transferrin. With inflammation or a chronic disease, serum iron also falls, but transferrin is then low as well and ferritin normal or high, so the saturation falls less sharply. During pregnancy and when using the contraceptive pill, the body makes more transferrin, which makes the percentage come out lower without a deficiency. Symptoms that go with iron deficiency are tiredness, shortness of breath during exertion, hair loss and restless legs.

After an abnormal result

With a saturation above 45 percent, the GP repeats the measurement, while fasting if in doubt, together with ferritin, CRP and liver values. If the saturation stays raised and the ferritin is also raised, the guideline recommends DNA testing for hemochromatosis (HFE genotyping) and, with a confirmed predisposition, a referral to the internist (specialist in internal medicine) or gastroenterologist; blood relatives are then eligible for testing. With a low saturation and a low ferritin, the cause of the iron deficiency is investigated.

Reliability

How reliable is the test?

For iron overload, the transferrin saturation is the most sensitive first test: according to the Dutch medical specialists' guideline (FMS) on hereditary hemochromatosis, a saturation above 45 percent, together with a raised ferritin, is the reason for DNA testing for the HFE predisposition. A raised ferritin without a raised saturation rarely points to hereditary iron overload. For iron deficiency, the saturation is less reliable than ferritin, because serum iron fluctuates strongly; the Dutch GP guideline (NHG) on anemia uses ferritin as the first test.

What can affect the result?

The value is calculated from the serum iron and therefore shares its daily rhythm and meal effect; according to the FMS guideline on hereditary hemochromatosis, fasting is not needed, but if in doubt a raised result is repeated while fasting, without iron or vitamin supplements in the 24 hours before.
Inflammation lowers iron and transferrin at the same time, which can make the saturation look normal in iron deficiency.
Pregnancy and the contraceptive pill raise transferrin and lower the saturation; liver disease and malnutrition lower transferrin and raise the saturation.
The 45 percent threshold applies to the predisposition for HFE hemochromatosis in people of European origin; the C282Y variant hardly occurs at all in people of Asian or African origin.

Preparation

Do not take iron tablets or a multivitamin with iron in the 24 hours before the sample is taken. They raise the value temporarily.

Who it is for

Who is the test useful for?

Useful for

Useful when iron overload is suspected: with hemochromatosis in the family, with a previously found raised ferritin, with unexplained joint symptoms, liver abnormalities or tiredness in middle age, always together with ferritin. Also useful to distinguish iron deficiency from anemia of a chronic disease when iron is low and there is inflammation. For an ordinary suspicion of iron deficiency, ferritin alone is usually enough; in adults without symptoms and without a family predisposition, routine measurement is not needed.

How common is it?

About 0.5 to 1.5 percent of the Northern European population has two copies of the C282Y variant, the predisposition for hereditary hemochromatosis; most of them have abnormal iron values, but only a small share develop symptoms, men usually from their forties and women later, after menopause. Iron deficiency is much more common: anemia due to iron deficiency in about 4 in 1000 people per year in general practice, mainly in women.

The FMS guideline on hereditary hemochromatosis and the NHG guideline on anemia

Drawbacks and risks

A single raised saturation due to a meal, supplements or the daily rhythm can cause unnecessary worry about iron overload; only a value that is raised on repeat testing counts.
A confirmed hereditary hemochromatosis also matters for parents, brothers, sisters and children (an incidental finding with consequences for blood relatives).

Get tested

Transferrin saturation: test panels

Transferrin saturation is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
Iron Status (Ferritin + Transferrin Saturation)
Ferritin and Transferrin Saturation; iron status.
€ 42,00
Blood draw
Transferrin Saturation
Transferrin saturation; iron transport saturation.
€ 35,00
Fingerstick
Iron Profile (Iron, Ferritin, Transferrin Saturation)
Combination of iron, ferritin, and transferrin saturation; iron status.
€ 35,00
Blood draw
Iron Profile (Iron, Transferrin Saturation, Ferritin)
Combination of iron, transferrin saturation, and ferritin; for iron status assessment.
€ 35,00
Blood draw
InsideTracker
InsideTracker Blood Analysis: analyze 48 biomarkers for complete health optimization and personalized recommendations.
€ 335,00
Blood draw
Endurance Sports
Complete blood count, iron status (ferritin, transferrin), kidney function, liver function, testosterone, and hs-CRP. For athletes and endurance sport participants.
€ 203,00
Blood draw
Whoop (Advanced Labs)
Comprehensive blood analysis with biomarkers that integrates directly with your WHOOP wearable for optimal performance and recovery.
€ 385,00

How reliable is the test?

Transferrin saturation