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Minerals

Iron in the blood: periods, pregnancy and what a low iron means

Iron is needed to make haemoglobin, the protein in red blood cells that carries oxygen. According to the NVKC, most of the iron in the body sits in the haemoglobin of the red blood cells.

During their period, according to the NVKC, women can lose so much blood that iron deficiency develops, and that can lead to anaemia. How much iron is in the blood only a blood test measures.

The unit for serum iron is micromoles per litre (µmol/l). Star-SHL uses 7 to 35 µmol/l for women aged 19 to 50, and 8 to 30 µmol/l for women aged 51 to 65.

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 35 umol/l
Reference ranges by group, in umol/l
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 35 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 · Female · 19–50 years 7–35 µmol/l
7 35
Star-shl · Female · 51–65 years 8–30 µmol/l
8 30
Star-shl · Female · 66–80 years 8–30 µmol/l
8 30
Star-shl · Female · 81 years and older 7–28 µmol/l
7 28
Unilabs · Female 10–25 µmol/l
10 25
Certe · Everyone · target values 10–30 umol/L
10 30
Diagnostiek voor U · Female 10–25 µmol/L
10 25
0 38.5 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

An iron determination gives the iron present in serum or plasma at that moment, as a concentration in micromoles per litre (µmol/l). According to the NVKC, iron is preferably determined together with transferrin, the transport protein for iron, to calculate which part of the transferrin carries iron: the transferrin saturation.

Star-SHL determines iron in serum, and Unilabs and Certe determine it in lithium heparin plasma.

Iron (Serum): why this value matters

Heavy blood loss from periods that are often long and heavy is, according to Thuisarts, the most common cause of anaemia in women, because the body then has too little iron. According to the NVKC, iron deficiency is the most common cause of anaemia in general.

According to Thuisarts, the body needs more iron during pregnancy than comes in with food, and heavy blood loss during an operation, childbirth or miscarriage can also leave too little iron.

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
Iron Status · €89,- · Anemia · €132,- · Prenatal Essentials · €199,-
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, iron is measured in anaemia, to establish whether a lack of iron is the cause, often together with ferritin. The NVKC recommends drawing blood in the morning before breakfast, because iron-rich food raises the value temporarily.

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

Low Levels

A low serum iron is common according to the NVKC, and in women with heavy blood loss during their period the iron shortage can turn into anaemia from iron deficiency (iron deficiency anaemia). In iron deficiency anaemia, according to the NVKC, ferritin is usually below 20 micrograms per litre.

According to Thuisarts, anaemia can cause a tired and weak feeling, dizziness, headache and less colour in the face.

High Levels

According to the NVKC, a high serum iron can point to iron overload when the transferrin saturation is also above 50%, and it can occur shortly after starting iron tablets. In hereditary iron overload, according to Thuisarts, symptoms can only appear once there is a lot of iron in the body, for example fatigue, abdominal pain and joint pain, mostly in the hands and wrists.

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 anaemia from too little iron, according to Thuisarts the treatment is iron pills. According to Thuisarts, stomach acid inhibitors make iron get into the body less well, and Thuisarts advises discussing that with the midwife or doctor.

Iron (Serum): frequently asked questions

Does the body need more iron during pregnancy?

During pregnancy, according to Thuisarts, the body needs more iron than comes in with food, and MedlinePlus names pregnancy as a possible cause of a lower iron.

Can the birth control pill affect the iron result?

According to MedlinePlus, birth control pills and oestrogens are on the list of medicines that can affect the result of a serum iron test. MedlinePlus advises not to stop any medicine before you have talked to a doctor.

What does a low transferrin saturation mean?

In anaemia from iron deficiency, the transferrin saturation, the percentage of transferrin that carries iron, is often below 10% according to the NVKC. According to the NVKC, that saturation usually lies between 20% and 45%.

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. Certe, Bepalingenwijzer (referentiewaarden per bepaling), bepalingenwijzer.certe.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenwijzer.certe.nl
  3. Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
  4. Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.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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