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Ferritin

Ferritin is the protein that stores iron in your cells, making it the most reliable blood test for your iron stores.

What is Ferritin?

Ferritin is the protein that stores iron inside your cells — mainly in the liver, spleen, and bone marrow. A small amount circulates in your blood, and as long as no inflammation is present that circulating level closely tracks your total iron reserves. This makes ferritin the most useful single blood test for catching iron deficiency before it turns into anaemia. The catch: ferritin also rises with infection, inflammation, liver injury, and heavy alcohol use — independent of how much iron you actually have. A 'normal' ferritin during active inflammation does not rule out an iron deficiency. Always read ferritin alongside serum iron, transferrin saturation, and CRP — never on its own.

Why is Ferritin relevant?

Iron deficiency is one of the most common and most missed reasons for fatigue, breathlessness on exertion, slow recovery, poor concentration, and hair shedding. These symptoms appear while stores are running down — often well before haemoglobin falls and anaemia shows up on a blood count. A low ferritin with an otherwise normal blood count is an early, actionable signal. Women with heavy periods, endurance athletes, pregnant people, and blood donors are most at risk. A persistently high ferritin also deserves attention rather than reassurance. In everyday practice it far more often signals inflammation, fatty liver, or poor metabolic health than iron overload. Transferrin saturation is the key distinguishing marker: a high ferritin paired with a persistently elevated transferrin saturation points toward iron overload and warrants medical evaluation.

Ferritin high or low — what it means

Ferritin is a snapshot. Infection, illness, hard training, or an inflammatory flare can push the value up — even when iron stores are actually low. Measure it when you are healthy and free of infection, and read it alongside transferrin saturation, serum iron, and CRP. A low ferritin almost always means depleted iron stores. The next question is why: menstrual or gut blood loss, insufficient dietary iron, poor absorption, or pregnancy are the usual drivers. Unexplained persistent iron deficiency in men or post-menopausal women should be investigated for a source of bleeding. Rebuilding stores via diet or supplementation takes time — retest after 8–12 weeks.

Ferritin reference ranges

MenLab-dependent reference for adult men30-300 µg/L
WomenLab-dependent reference for adult women15-200 µg/L
Iron deficiency confirmedDutch GP guideline (NHG): confirms iron deficiency<15 µg/L
Grey zoneRequires additional data such as MCV and an inflammation marker15-100 µg/L
Sensitive lower boundA growing number of Dutch labs (e.g. OLVG Lab) use a 30 µg/L lower bound, equal for men and women: below this, iron deficiency can already be present, even within the 'normal' range<30 µg/L

Cut-offs differ by lab, method, sex and age. Ferritin is an acute-phase protein: infection or inflammation can push it falsely high, masking an iron deficiency. Always read ferritin together with serum iron, transferrin saturation and hs-CRP — never on its own. Values in µg/L are numerically equal to ng/mL.

Educational information only — not medical advice. Consult a healthcare professional for clinical decisions.

Read about our scientific approach →Read the guide: Energy →

Frequently asked questions

What is a normal ferritin level?

As a lab-dependent guide, ferritin in adult men is roughly 30–300 µg/L and in women 15–200 µg/L (µg/L equals ng/mL numerically). Exact limits vary by lab, sex and age. Important: a growing number of Dutch labs use a more sensitive lower bound — a value under 30 µg/L is often already treated as iron deficiency, even if it falls within the printed 'normal' range.

What does a low ferritin mean?

A low ferritin almost always means depleted iron stores. The Dutch GP guideline (NHG Anaemia standard) treats ferritin below 15 µg/L as confirming iron deficiency; between 15 and 100 µg/L additional data are needed (such as MCV and an inflammation marker). It's an early signal: symptoms like fatigue, breathlessness on exertion, slow recovery and hair loss can appear before haemoglobin drops. The next question is always why — think menstrual or gastrointestinal blood loss, too little dietary iron, poor absorption or pregnancy.

What does a high ferritin mean?

A value above roughly 100 µg/L makes iron-deficiency anaemia unlikely. In everyday practice a persistently high ferritin points more often to inflammation, fatty liver, metabolic syndrome or alcohol than to true iron overload. Transferrin saturation helps distinguish: a persistently raised saturation (roughly above 45% in women and 50% in men) together with high ferritin points toward iron overload (such as hereditary haemochromatosis).

When is a ferritin level concerning?

A single ferritin value is a starting point, not a verdict — ideally measure when you're infection-free and well, and read it alongside transferrin saturation, serum iron and hs-CRP. An unexplained, persistent iron deficiency in men or in post-menopausal women should be investigated for a source of blood loss. A clearly or persistently high ferritin — especially with a high transferrin saturation — warrants a doctor's review. After addressing it through diet or supplementation, stores rebuild slowly: only retest after 8–12 weeks.

Related biomarkers

Transferrin Saturation
Transferrin saturation is the percentage of your transferrin loaded with iron and shows how much iron is available.
Serum Iron
Serum iron is a snapshot of the amount of iron circulating in your blood right now, bound to its transport protein.
Transferrin
Transferrin is the transport protein that carries iron through your blood to your cells.
C-Reactive Protein (CRP)
CRP is a protein your liver makes in response to inflammation, serving as a broad marker of inflammation in your body.

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