What is iron deficiency?
Your body keeps iron as a reserve and uses it to make haemoglobin, the protein with which red blood cells carry oxygen, and to keep the muscles and the energy production of every cell running. If that reserve runs out, you notice nothing at first: the body simply keeps making haemoglobin and meanwhile drains the store. Only when the store is truly empty does production suffer, and the red blood cells become smaller and paler. That is why iron deficiency becomes visible in two steps. Ferritin falls first, because that is the store gauge. Then the blood count changes: MCV falls, RDW rises because old and new cells exist side by side, and eventually haemoglobin falls. Anyone who looks only at that last number therefore sees the deficiency only in the final stage, while tiredness and restless legs can already be there with an empty store. Iron only comes in through food, and the body cannot get rid of it deliberately: what is lost, is lost through blood. That is why iron deficiency in adults is almost always a matter of loss outrunning intake, heavy periods first of all, and only then of a gut absorbing less or a body temporarily asking for more, in pregnancy or with a lot of endurance sport.
Which blood values show iron deficiency?
Every value below has its own page with the reference ranges of four Dutch labs.
| Value | What it shows | Points here when |
|---|---|---|
| Ferritindefining | How much iron your body has in store. The first value to fall. | low |
| Transferrin Saturationdefining | How much of your transport iron is actually occupied. Stays usable when inflammation distorts ferritin. | low |
| Transferrin | The transport protein itself. Your body makes more of it when iron is short. | high |
| Serum Iron | The iron circulating in your blood right now. Swings widely over the day. | low |
| MCV | The average size of your red blood cells. Iron shortage makes them smaller. | low |
| MCH | How much haemoglobin an average red blood cell carries. | low |
| RDW | How much your red blood cells differ from each other in size. Often rises before MCV falls. | high |
What are the symptoms of iron deficiency?
These complaints are described for iron deficiency in guidelines and research. None of them is exclusive to it: the same complaints fit many other explanations, and an abnormal value can exist without any of them.
An early iron deficiency can exist without complaints for a long time: the body first quietly draws on the store, and complaints follow late or not at all.
- Tiredness that rest does not liftin research
Also without anaemia: in controlled studies of women with low ferritin, fatigue eased after iron.
Also described at anaemia, underactive thyroid, vitamin B12 deficiency, low testosterone.
- Restless legs, mostly in the eveningin research
The link is consistent enough that restless-legs guidelines advise checking ferritin.
- Trouble concentratingin research
Also described at underactive thyroid, vitamin B12 deficiency, low testosterone.
- Hair loss and brittle nailsin research
Described in research; the evidence here is more mixed than for fatigue.
Also described at PCOS.
- Craving non-food items such as ice or soilin research
Rare but classically described; it usually disappears once iron is replenished.
- Pale skin, most visible inside the lower eyelidin the guideline
Belongs to the stage where the deficiency leads to anaemia; that page explains this complaint.
- Short of breath during effort you normally handle easilyin the guideline
Belongs to the stage where the deficiency leads to anaemia; that page explains this complaint.
A complaint points in more than one direction, and a measurement explains no complaint: blood testing shows where your values stand, the reading and the diagnosis belong with your GP. The complaint list follows the Dutch GP guideline on anaemia (NHG) and research on iron deficiency without anaemia.
What causes iron deficiency?
Blood loss
More iron leaves the body than comes in. In adults this is the most common route.
- Heavy or prolonged menstruation
- Bleeding in the stomach or bowel, which is not always visible
- Donating blood regularly
Reduced absorption
The iron is there in the diet, but the bowel takes up too little of it.
- Coeliac disease or another bowel condition
- Long-term use of acid-suppressing medication
- After gastric surgery
Higher demand
Intake is normal, but the body temporarily asks for more than usual.
- Pregnancy and the period after birth
- Growth during puberty
- Intensive endurance sport
Low intake
Rarely the only cause in adults, but a factor that amplifies the other three.
- A diet with little or no meat, without deliberate supplementation
What is iron deficiency confused with?
Each with the one value that tells the two apart.
Anaemia
Iron deficiency is about the store, anaemia is about haemoglobin. You can have an empty iron store with a normal haemoglobin, and anaemia can have causes other than iron.
Distinguishing value: Hemoglobin
Vitamin B12 deficiency
Both cause tiredness, but MCV points the other way: iron shortage makes red blood cells smaller, a B12 deficiency makes them larger.
Distinguishing value: MCV
Anaemia of chronic disease
Here ferritin is normal or even raised while transferrin saturation stays low. The iron is present but held back.
Distinguishing value: Transferrin Saturation
What you do about iron deficiency
Refill the store and close the leak. Eat iron-rich food daily: red meat, fish and poultry contain the form the body absorbs best, and legumes, whole grains, nuts and green leafy vegetables the plant form, which absorbs better with some vitamin C alongside, such as pepper, citrus or kiwi. Do not drink coffee and tea with the meal, because they inhibit absorption, and keep dairy and calcium tablets an hour away from the iron-rich meal. If the store is truly empty, food usually does not catch up and tablets are the way: one tablet a day or every other day, on an empty stomach if your stomach tolerates it, for three to six months, because haemoglobin recovers in weeks and the store only after that. With heavy periods it helps to tackle those, with the pill or a coil, and with blood loss you do not see the gut should be checked, certainly above fifty. Anyone who eats plant-based, does sport or is pregnant plans iron deliberately. Measure again after three months: ferritin for the store, haemoglobin for the effect. A ferritin that does not rise while you take tablets means the leak is larger than the refill or the gut is not absorbing it.
From which ferritin does a lab call it low?
This is what the four largest Dutch labs publish themselves, side by side.
30 – 120µg/L
Between 6 and 30 and between 120 and 175 it depends on the lab, because each sets its limits on its own method and population. Above 175 every lab calls it abnormal.
every lab calls 30 – 120 µg/L normal. Between 6 and 30 and between 120 and 175 it depends on the lab.
Every age group per lab
| Lab | Group | Reference range |
|---|---|---|
| Unilabs(Saltro, Medlon, SHO, Atalmedial)2026 | Men 15–20 yrs | 11–135 µg/L |
| Men 20–30 yrs | 19–200 µg/L | |
| Men 30–50 yrs | 19–305 µg/L | |
| Men 50–75 yrs | 15–460 µg/L | |
| Women 18–40 yrs | 6–120 µg/L | |
| Women 40–55 yrs | 6–180 µg/L | |
| Women 55–75 yrs | 9–250 µg/L | |
| Men 75+ | 19–460 µg/L | |
| Women 75+ | 11–350 µg/L | |
| Star-shl2026 | Men | 30–400 µg/L |
| Women | 15–150 µg/L | |
| Certe2026 | Men 18+ | 30–409 µg/L |
| Women 18–50 yrs | 30–175 µg/L | |
| Women 50+ | 30–328 µg/L | |
| Clinical Diagnostics2026 | Men | 25–250 µg/L |
| Women under 45 | 20–150 µg/L | |
| Women 45+ | 20–250 µg/L |
How to get iron deficiency measured
- Fasting
- No fasting needed. Eating makes no difference to ferritin or the red cell values.
- Material
- Venous blood, drawn at one of our collection points.
- Results
- Results within 24 hours of analysis, in the app.
- Referral
- No referral from a GP required.
- Which test
- The Iron & fatigue test (€99, single test) measures the values on this page.
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
From which ferritin do you speak of iron deficiency?
Below 30 µg/L the store is in practice running out, and that is also the lower limit of the strictest lab. Below that it differs per report: the lower limit runs for an adult woman from 6 µg/L to 30, so the same 12 µg/L is normal at one lab and too low at another. So look at the whole picture: a ferritin below 30 with complaints or a falling haemoglobin is a deficiency, whichever lab made the report.
Can you have iron deficiency without anaemia?
Yes, and that is the rule rather than the exception. The store runs out before the production of red blood cells suffers, so your ferritin can already be low while your haemoglobin still sits within the band. Tiredness and restless legs can already be there in that stage. Anyone who looks only at haemoglobin misses that stage; so always read ferritin together with the blood count.
What does a normal ferritin mean during an inflammation?
That the store can still be empty. Ferritin is also an inflammatory protein and rises with inflammation, infection and liver disease, so the value looks normal while in reality there is little iron. In that situation transferrin saturation says more, because it is less sensitive to inflammation, and CRP shows whether an inflammation is at play. Measure them together, so the one value corrects the other.
What about iron deficiency during pregnancy?
The need for iron rises sharply in pregnancy, because your body makes more blood and the child builds its own store. Anyone who starts pregnancy with a low store almost always runs short. The midwife therefore checks haemoglobin as standard around week twelve and week thirty. The bands on this page apply outside pregnancy; in that period your midwife reads the result with other limits.
Can iron deficiency cause hair loss?
It is described, but the evidence is more mixed than for tiredness. Hair follicles are among the fastest-dividing cells of the body, and those notice an empty store first; that explains the thinking behind it. The loss is then diffuse, thinner over the whole head instead of in one spot. With hair loss ferritin is often measured and replenished if it is low, but a low store is not the only possible explanation.
Sources
- 1.NHG-Standaard Anemie. 2024. richtlijnen.nhg.org
- 2.Unilabs test directory, ferritin. 2026. bepalingenklapper.nl
- 3.Star-shl test directory, ferritin. 2026. star-shl.nl
- 4.Certe test directory, ferritin. 2026. bepalingenwijzer.certe.nl
- 5.Clinical Diagnostics test guide, ferritin. 2026. clinicaldiagnostics.nl
This page explains what a result means. It is not a diagnosis and not treatment advice. Discuss complaints or an abnormal value with your doctor.
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