Biomarkers

Ferritin Blood Test: The Iron-Storage Marker That Falls First

Medically reviewed by Longevity Benchmark Editorial Last reviewed 2026-08-23

A ferritin blood test estimates iron stores. Labs publish roughly 15 to 205 ng/mL for females and 30 to 566 for males. Why inflammation misleads.

Ferritin is the protein iron is stored inside, and the small amount circulating in blood tracks how much iron you have banked. That makes a ferritin blood test a measure of reserves rather than of the iron currently in transit. Reserves are spent before anything else changes, which is why ferritin falls earlier than serum iron and earlier still than a blood count.

The Verdict

Ferritin estimates iron stores. Cleveland Clinic publishes roughly 15 to 205 ng/mL for females and 30 to 566 ng/mL for males, and the male range is far wider at the top. Other laboratories publish materially different bands, so read your result against the range printed on your own report. The complication that defines this marker is that ferritin is also an acute-phase reactant: it rises with inflammation, so a normal-looking result can sit on top of genuinely depleted stores. Ferritin is read alongside an inflammatory marker and, where they disagree, alongside transferrin saturation.

What a ferritin blood test measures

Iron is too reactive to circulate freely, so the body keeps it bound. Storage iron sits inside ferritin, a hollow protein shell held mostly in the liver, spleen and bone marrow. A small quantity of ferritin leaks into serum in rough proportion to the size of those stores, and that is what the test detects.

Iron deficiency develops in stages, and ferritin marks the first one. Stores deplete, and ferritin falls while everything else still reads normal. Circulating iron falls next, and transferrin saturation drops. Only in the final stage does haemoglobin fall far enough to produce anaemia. Someone can be substantially iron-depleted, symptomatic, and have an entirely normal full blood count.

Results are reported in nanograms per millilitre or in micrograms per litre. The two units are numerically identical, so a report reading 42 µg/L and one reading 42 ng/mL say the same thing.

Ferritin levels: reference ranges by sex

Group	Range	Notes
Females, Cleveland Clinic reference range	Roughly 15 to 205 ng/mL	This is Cleveland Clinic's published band specifically, rather than a consensus figure. Menstrual iron loss is why the female range sits lower and why the lower limit is so often reached.
Males, Cleveland Clinic reference range	Roughly 30 to 566 ng/mL	Cleveland Clinic's published band. Much wider at the top. A result of 400 is inside the printed range and still worth a second look alongside other markers.
Children, 6 months to 15 years	Roughly 12 to 140 ng/mL	Paediatric ranges differ from adult ones and are not interchangeable.
Commonly argued optimal band	Roughly 50 to 150 ng/mL, and 50 to 100 for premenopausal women	An argued target rather than a diagnostic threshold, on the reasoning that symptoms are common in the lower part of the printed range. Contested, and not a reason to self-treat.
Widely used deficiency cut-off	Below roughly 30 ng/mL	Treated as evidence of depleted stores in most guidance, well above the bottom of the printed reference range. Where inflammation is present a higher cut-off is used, as set out in the TIBC guide.

The gap between the male and female ranges is the largest of any marker on a routine panel, and it is a consequence of menstrual iron loss shifting the female reference population downward. Reading a female result against a male range, which some consumer reports do when they print one combined band, makes a genuinely low result look unremarkable.

Ferritin reference ranges vary between laboratories more than almost any other routine marker, so the band printed on your report may not match the one above. Other commonly published sets include a combined adult band of roughly 30 to 400 ng/mL, and lower limits stated anywhere between 12 and 30 ng/mL. Our own biomarker hub cites the 30 to 400 band, and normal vs optimal uses lower bounds of 12 to 30 for men and 12 to 15 for premenopausal women. The disagreement is real rather than an error in one source: each laboratory derives its own range from its own reference population and assay.

The Reference Range Is Wider Than The Deficiency Threshold

This is the practical consequence of that spread, and it is the thing most likely to mislead you. The bottom of a printed reference range marks the level at which bone-marrow iron stores are effectively absent, which is a threshold for diagnosing iron deficiency anaemia rather than a floor for adequate function. Most guidance treats a ferritin below roughly 30 ng/mL as evidence of depleted stores, and symptoms including fatigue, hair shedding and reduced exercise tolerance are commonly reported below 30 to 50 ng/mL. A woman with a ferritin of 20 is therefore inside Cleveland Clinic's printed female range and below the threshold most clinicians would act on. That is not a contradiction between sources. It is the difference between a statistical description of a population and a clinical decision point, which is the same distinction our normal vs optimal guide draws for every marker. Going the other way, that guide treats a ferritin above roughly 300 ng/mL in men or 200 in women as worth investigating, well inside the printed upper limits above.

Ferritin and serum iron are different questions

A ferritin blood test and an iron blood test answer different things, and the two are frequently treated as interchangeable. Serum iron measures what is circulating at the moment of the draw. It swings with the time of day and rises for hours after an iron-containing meal or a supplement, which makes a single value unstable.

Ferritin measures the reserve behind that circulating iron and changes over weeks rather than hours. The two can disagree in an informative way. Ferritin can be low while serum iron reads normal, because the body draws down stores to keep circulating levels up. That combination describes depleted reserves that have not yet produced a visible shortfall. Total iron binding capacity and transferrin saturation complete the picture by describing how much of the transport capacity is occupied, and those are covered in the TIBC and iron saturation guide.

Low ferritin: what depletes the stores

Cause	How often it explains a result	Notes
Menstrual blood loss	The most common cause in menstruating people	Heavy periods deplete stores steadily, and the result often sits below range long before a blood count changes.
Inadequate dietary iron	Common	Plant-source iron is absorbed less efficiently than the form in meat, so intake and absorption are separate questions.
Impaired absorption	Frequently missed	Coeliac disease, gastric surgery, and long-term acid-suppressing medication all reduce iron uptake. Testing for coeliac disease is a standard part of the workup for unexplained iron deficiency.
Gastrointestinal blood loss	The one not to miss	Slow bleeding from the gut can be invisible. Unexplained iron deficiency in a man, or in a woman after menopause, warrants medical assessment rather than a supplement.
Pregnancy	Expected	Iron demand rises substantially. Pregnancy uses its own thresholds and its own management.
Frequent blood donation	Common and easy to overlook	Each donation removes a meaningful quantity of iron, and stores can take months to rebuild.

A low ferritin identifies a state and says nothing about why. In menstruating people the cause is usually apparent. Outside that group, and particularly in men and in women after menopause, unexplained iron deficiency is investigated for a source of blood loss rather than corrected with a supplement. This page gives no guidance on iron dosing.

High ferritin: why inflammation is the usual answer

Cause	How often it explains a result	Notes
Inflammation or infection	The most common reason by far	Ferritin rises as part of the acute-phase response. A high result during or shortly after an illness usually describes the illness.
Hereditary haemochromatosis	Uncommon, and the one that changes management	An inherited disorder of iron absorption leading to genuine overload. Transferrin saturation and genetic testing sort it from an inflammatory rise.
Liver disease	Common	Fatty liver disease and alcohol-related liver damage both raise ferritin, often with raised liver enzymes alongside.
Metabolic syndrome	Common and under-recognised	A modestly raised ferritin frequently accompanies insulin resistance and fatty liver rather than iron overload.
Chronic kidney disease and some cancers	Uncommon	Both feature in the differential for a persistently high result with no simpler explanation.

Why A Normal Ferritin Can Sit On Top Of Real Deficiency

Ferritin moves in two directions for two unrelated reasons. Iron deficiency pushes it down. Inflammation pushes it up, because ferritin is part of the acute-phase response the body mounts during infection, injury and chronic inflammatory illness. In someone who has both, the two effects offset and the result lands in the middle of the reference range while the stores are genuinely empty. This is the single most common way iron deficiency is missed on a routine panel. Two habits address it: draw ferritin alongside an inflammatory marker such as hsCRP so a raised ferritin can be read in context, and use transferrin saturation as a tiebreaker when ferritin and symptoms disagree. The adjusted thresholds that apply in the presence of inflammation are set out in the TIBC guide, which carries this interaction in more detail.

What ferritin means in combination

Low ferritin + low transferrin saturation: iron deficiency with little ambiguity. The question becomes where the iron is going.
Low ferritin + normal haemoglobin: iron depletion without anaemia. Fatigue and reduced exercise capacity are commonly reported here, and a full blood count alone would report everything as normal.
Normal or high ferritin + high hsCRP: the inflammatory pattern. The ferritin result describes the inflammation and cannot be read as a statement about iron stores.
High ferritin + high transferrin saturation: the combination that raises genuine iron overload and haemochromatosis, and the one that most changes what happens next.
High ferritin + raised ALT or GGT: points toward liver involvement, whether from fatty liver disease or alcohol.
Low ferritin + high RDW + low MCV: the red-cell picture of established iron deficiency, with small cells of uneven size.

How and when to test ferritin

Avoid testing during or just after an illness. The acute-phase rise distorts the result more than anything else on this list, and it can take weeks to settle.
Order an inflammatory marker alongside it, so a normal or raised ferritin can be interpreted rather than assumed.
Follow your laboratory's instruction on fasting and on pausing iron supplements. Ferritin itself is not especially food-sensitive, and the serum iron commonly drawn with it is.
Use the same laboratory when repeating, since assay and reference-range differences between labs are large enough to look like real change.
Allow enough time before retesting. Stores rebuild over months, so a repeat at a few weeks tells you little.

When a result warrants seeing a physician

Any low ferritin in a man, or in a woman after menopause, where blood loss is investigated before iron is replaced.
A persistently high ferritin with a high transferrin saturation, which raises haemochromatosis.
A low ferritin alongside heavy menstrual bleeding, which has treatable causes of its own.
Any abnormal iron result in pregnancy, where different thresholds and different management apply.
Before starting iron on the strength of a number, since supplementing iron in someone with iron overload causes harm.

Ferritin answers one question well and only in context. It tells you how much iron is in reserve, provided nothing inflammatory is pushing it upward at the same time. Draw it with an inflammatory marker, read it against the range for your sex, and take the question of why it is low or high to a clinician who can see the rest of the panel.

Frequently Asked Questions

What does a ferritin blood test measure?

Ferritin is the protein your body stores iron inside, and a small amount of it circulates in blood in proportion to how much iron you have banked. Measuring serum ferritin therefore estimates your iron stores rather than the iron in transit. That is what makes it the first test for suspected iron deficiency: stores are depleted before the blood count or the circulating iron level changes, so ferritin falls earliest. The result is reported in nanograms per millilitre, and micrograms per litre is the same number under a different name.

What is a normal ferritin level?

Cleveland Clinic publishes roughly 15 to 205 ng/mL for females and roughly 30 to 566 ng/mL for males, with a paediatric range of roughly 12 to 140 ng/mL for children aged 6 months to 15 years. Exact limits vary between laboratories, because each derives its own range from its own reference population and assay. The male range is far wider at the top, so a single number means different things depending on which range your laboratory applied. An optimal band nearer 50 to 150 ng/mL is commonly argued for, and that is an argument about where symptoms cluster rather than a diagnostic threshold.

Is a ferritin blood test the same as an iron test?

No, and the difference explains a lot of confusing results. Serum iron measures the iron circulating in your blood right now, which swings with what you ate and with the time of day. Ferritin estimates what is in storage, which changes slowly. A full iron panel usually adds total iron binding capacity and transferrin saturation, which together describe how much carrying capacity is in use. Ferritin can be low while serum iron reads normal, because the body pulls from stores to keep circulating levels up. The relationship between these markers is covered in the guide to TIBC and transferrin saturation.

Why is my ferritin high?

The most common reason is inflammation. Ferritin behaves as an acute-phase reactant, meaning it rises during infection, injury and inflammatory illness regardless of how much iron you have. A result drawn during or shortly after an illness commonly reads high for that reason alone. Other causes include liver disease, heavy alcohol use, metabolic syndrome and chronic kidney disease. Genuine iron overload from hereditary haemochromatosis is less common and is the possibility that most changes management, which is why a persistently high ferritin is usually followed with transferrin saturation and, where indicated, genetic testing.

Does a ferritin blood test require fasting?

Ferritin itself does not require fasting, and it is frequently drawn as part of a panel that does. Iron studies are a different matter: serum iron varies through the day and rises after an iron-containing meal or supplement, so laboratories often ask for a morning draw and for iron supplements to be paused beforehand. Follow the instruction your laboratory gives, since protocols differ. The more useful preparation is to avoid testing during or just after an illness, because that shifts ferritin more than breakfast does.

Can ferritin be normal and iron still be low?

Yes, and this is the most common way iron deficiency gets missed. Because inflammation pushes ferritin up while iron deficiency pushes it down, the two can cancel out and produce a result in the middle of the reference range in someone whose stores are genuinely depleted. This is why ferritin is interpreted alongside an inflammatory marker such as hsCRP, and why transferrin saturation is useful when the two conflict. The thresholds that apply when inflammation is present are higher than the usual ones, and they are set out in the TIBC guide.

Should I take iron if my ferritin is low?

That is a decision for the clinician who ordered the test, for two reasons. The first is that a low ferritin is a finding rather than a diagnosis, and the question of why iron is being lost matters more than the number. Unexplained iron deficiency in a man, or in a woman after menopause, is investigated for a source of blood loss before it is treated. The second is that iron supplementation carries real risk in people who turn out to have haemochromatosis, and taking iron without a test can do harm. Ferritin is the marker that answers whether iron is warranted, which is why testing comes before supplementing.