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Minerals

Iron in the blood: what serum iron measures, the limits and what a high or low value means

Iron is a mineral the body needs to make haemoglobin, the protein red blood cells use to bind and carry oxygen. Iron is taken up in the gut, carried in the blood by the transport protein transferrin and stored as a reserve in the liver in the protein ferritin.

With too little iron the body cannot make enough haemoglobin and the cells receive less oxygen; with hereditary iron overload (haemochromatosis) the body instead keeps taking up too much iron. How much iron is in the blood can only be measured with a blood test.

Serum iron is measured in micromoles per litre (µmol/l). For people aged 19 to 50, Star-SHL uses 8 to 39 µmol/l for men and 7 to 35 µmol/l for women.

Doctor's Assessment Included

Serum iron is the amount of iron in the blood at the moment of the draw; in healthy people it averages about 20 µmol/l according to the NVKC. Star-SHL and Unilabs use separate limits for men and women, Star-SHL also per age, and Certe one limit for everyone.

  • The NVKC advises drawing blood preferably in the morning before breakfast, because iron-rich food raises iron temporarily.
  • According to the NVKC, iron is preferably judged with the transferrin saturation, which usually lies between 20% and 45%; with an iron (much) higher than 20 µmol/l and a saturation above 50%, there can be iron overload.
  • Certe uses one iron limit of 10 to 30 µmol/l for all ages and both sexes, and calls it target values.

Reference Ranges

See the value that applies to you:

Choose male or female — this range differs by sex.

Enter your age — this range changes with age.

This range also depends on context such as cycle phase or sample material; the highlighted rows apply to your group.

Your reference range
umol/l
6 39 umol/l
Reference ranges by group, in umol/l
Male · 6–12 years 7–30 umol/l
7 30
Male · 13–18 years 9–35 umol/l
9 35
Male · 19–50 years 8–39 umol/l
8 39
Male · 51–65 years 8–35 umol/l
8 35
Male · 66–80 years 7–31 umol/l
7 31
Male · 81 years and older 8–29 umol/l
8 29
Female · 6–12 years 7–31 umol/l
7 31
Female · 13–18 years 6–35 umol/l
6 35
Female · 19–50 years 7–35 umol/l
7 35
Female · 51–65 years 8–30 umol/l
8 30
Female · 66–80 years 8–30 umol/l
8 30
Female · 81 years and older 7–28 umol/l
7 28
6 39 umol/l

Source: NVKC Reference population: Dutch general-practice population (NUMBER, n = 7,574,327)

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

Iron (Serum): what Dutch laboratories use

Reference ranges by group, in umol/l
Star-shl · Male · 19–50 years 8–39 µmol/l
8 39
Star-shl · Female · 19–50 years 7–35 µmol/l
7 35
Star-shl · Male · 51–65 years 8–35 µmol/l
8 35
Star-shl · Female · 51–65 years 8–30 µmol/l
8 30
Star-shl · Male · 66–80 years 7–31 µmol/l
7 31
Star-shl · Female · 66–80 years 8–30 µmol/l
8 30
Star-shl · Male · 81 years and older 8–29 µmol/l
8 29
Star-shl · Female · 81 years and older 7–28 µmol/l
7 28
Unilabs · Male 14–35 µmol/l
14 35
Unilabs · Female 10–25 µmol/l
10 25
Certe · Everyone · target values 10–30 umol/L
10 30
Diagnostiek voor U · Male 14–35 µmol/L
14 35
Diagnostiek voor U · Female 10–25 µmol/L
10 25
0 42.9 umol/l

Source: Star-shl

Source: Unilabs

Source: Certe

Source: Diagnostiek voor U

Each value as the laboratory itself publishes it, retrieved in 2026.

Iron (Serum): what this test measures

The iron test measures how much iron is in serum or plasma, the liquid part of the blood without the blood cells, in micromoles per litre (µmol/l). According to the NVKC, most of the body's iron is not in that fluid but in the haemoglobin of the red blood cells.

Star-SHL measures iron in serum, Unilabs and Certe in lithium heparin plasma. According to the NVKC, iron is preferably measured together with transferrin; both values give the transferrin saturation, the percentage of transferrin that carries iron, which usually lies between 20% and 45%.

Iron (Serum): why this value matters

According to the NVKC, serum iron helps to detect conditions that come with iron deficiency and anaemia, or with too much iron, such as iron overload (haemochromatosis). According to the NVKC, iron deficiency is the most common cause of anaemia, in which a person has too few red blood cells.

In hereditary iron overload the body keeps taking too much iron from food and drink, according to Thuisarts, and that iron can damage organs such as the liver, the pancreas, the heart and the joints. According to the NVKC, the transferrin saturation can establish whether there is iron deficiency or iron overload.

Iron (Serum): how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Which test
Vitamin & mineral checkup · €229,-
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Iron (Serum): how to prepare

  1. Better not right after an infection

    Recommended

    After an infection or vaccination this value can be off for 2 weeks. Preferably draw once you are fully recovered.

  2. Preferably fasting

    Recommended

    Coming fasting gives a slightly cleaner value, but it is not required. If it suits you, eat nothing from 22:00 the evening before and drink only water.

  3. Preferably in the morning

    Recommended

    A morning draw makes this value easiest to compare with its reference range. Plan the draw before 10:00 if you can.

  • Water is always fine. Drink as usual beforehand, it makes the draw easier.
  • Take your usual medication, unless your own doctor told you otherwise.

Iron (Serum): when is testing worthwhile?

According to the NVKC, serum iron is measured in anaemia, to check whether it comes from a shortage of iron, and with symptoms that fit iron overload, such as fatigue, joint complaints and diabetes. The NVKC advises drawing the blood preferably in the morning before breakfast, because iron-rich food, such as apple syrup or spinach, raises iron temporarily.

According to MedlinePlus, certain medicines can affect the result, including antibiotics, birth control pills and oestrogens, blood pressure medicines, cholesterol medicines, gout medicines and testosterone. MedlinePlus advises not to stop any medicine before talking to your doctor.

Iron (Serum): symptoms of a high or low value

Low Levels

A low serum iron is common according to the NVKC, for example in women who lose a lot of blood during their period, and it can lead to anaemia from iron deficiency. In iron deficiency anaemia, according to the NVKC, the transferrin saturation is often below 10% and ferritin usually below 20 micrograms per litre.

With anaemia, Thuisarts names these symptoms: feeling tired and weak, feeling short of breath on stairs or during sport, dizziness, feeling faint, a heartbeat you can feel, sweating, headache, ringing in the ears and less colour in the face.

High Levels

According to the NVKC, a high serum iron with a transferrin saturation above 50% can point to iron overload, a disease in which the gut constantly takes up too much iron from food. In iron overload, according to the NVKC, ferritin is usually strongly raised, above 500 micrograms per litre.

People with hereditary iron overload often notice little or nothing, according to Thuisarts, and symptoms can only appear once there is a lot of iron in the body, usually between 40 and 50: for example fatigue, pain in the joints of the hands and wrists, abdominal pain, a grey-brown skin, heart complaints and, in men, erectile dysfunction. According to the NVKC, a rise can also occur in people who have just started taking iron tablets.

Iron (Serum): causes of a low or high value

What lowers the value

  • Heavy periods

    According to the NVKC, women can lose so much blood during their period that iron deficiency develops, and that can lead to anaemia.

  • Long-term blood loss through the stomach or bowel

    According to Thuisarts, losing small amounts of blood through the stomach or bowel over a long time is often the cause of too little iron in people over 50.

  • Too little iron in the diet

    According to Thuisarts, years of eating very little food that contains iron can lead to too little iron in the body.

  • Poor uptake in the gut

    According to Thuisarts, the body can have too little iron with a disease that makes it harder for iron to get into the body through the gut.

  • Pregnancy

    According to Thuisarts, the body needs more iron during pregnancy than comes in with food.

What raises the value

  • Hereditary iron overload (haemochromatosis)

    With an iron (much) higher than 20 µmol/l and a transferrin saturation above 50%, there can be iron overload according to the NVKC, in which the body constantly takes up too much iron from food.

  • Recently started iron tablets

    According to the NVKC, a rise can also occur in people who have just started taking iron tablets.

  • Iron-rich meal before the draw

    Iron-rich food, such as apple syrup or spinach, gives a temporary rise according to the NVKC; that is why blood is preferably drawn in the morning before breakfast.

  • Inflammation of the liver (hepatitis)

    According to MedlinePlus, a higher-than-normal iron may be a sign of inflammation of the liver.

  • Frequent blood transfusions

    According to MedlinePlus, a higher-than-normal iron may be a sign of frequent blood transfusions.

Iron (Serum): lifestyle and this value

With a low iron and anaemia, according to Thuisarts the GP can find what causes the anaemia with blood tests, and sometimes an examination of the stomach or bowel follows, for example in people over 50. With too little iron despite a healthy diet, Thuisarts says iron pills are needed, and vitamin C from an orange or kiwi lets the body take up more iron, while coffee, tea and milk reduce the uptake.

In hereditary iron overload, the treatment according to Thuisarts is usually bloodletting, the regular removal of half a litre of blood. In hereditary iron overload, Thuisarts advises no or little red meat, no fruit or fruit juice with vitamin C at meals and no alcohol.

Iron (Serum): frequently asked questions

When is serum iron best drawn?

According to the NVKC, serum iron is preferably drawn in the morning before breakfast, because iron-rich food raises the value temporarily. According to MedlinePlus too, the result can change depending on how recently someone has taken in iron.

What is the difference between serum iron and ferritin?

Serum iron is the iron in the blood at the moment of the draw, bound to the transport protein transferrin, while ferritin is the protein in which the liver keeps the iron reserve. The NVKC puts ferritin usually below 20 micrograms per litre in anaemia from iron deficiency and often above 500 micrograms per litre in iron overload.

Can a raised iron come from iron tablets?

Yes, according to the NVKC a raised serum iron can occur in people who have just started taking iron tablets. MedlinePlus also names iron poisoning and frequent blood transfusions, among others, as possible causes of a higher iron.

Iron (Serum): sources

  1. den Elzen WPJ, Brouwer N, Thelen MH, Le Cessie S, Haagen I-A, Cobbaert CM. NUMBER: standardized reference intervals in the Netherlands using a 'big data' approach. Clin Chem Lab Med 2018;57(1):42-56. (retrieved 2026) doi.org
  2. Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
  3. Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.nl
  4. Certe, Bepalingenwijzer (referentiewaarden per bepaling), bepalingenwijzer.certe.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenwijzer.certe.nl
  5. Diagnostiek voor U, eLabgids (Referentiewaarden DvU), diagnostiek.getincontrol.eu, geraadpleegd 2026-10-01 (retrieved 2026) diagnostiek.getincontrol.eu
  6. NVKC, Alles over testen: IJzer, allesovertesten.nl, geraadpleegd 2026-10-16 (retrieved 2026) allesovertesten.nl
  7. NHG, Thuisarts.nl: Ik heb bloedarmoede, geraadpleegd 2026-10-12 (retrieved 2026) thuisarts.nl
  8. MedlinePlus Medical Encyclopedia: Serum iron test, U.S. National Library of Medicine, geraadpleegd 2026-10-12 (retrieved 2026) medlineplus.gov

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Iron (Serum)

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