Understanding your bloodwork
Ferritin Is High But My Iron Is Low — What's Going On?
Ferritin usually tracks how much iron your body has in store. When it climbs while the iron itself looks scarce, the number has stopped answering that question and started asking a different one.
The short answer
Ferritin is a storage protein, and it also rises whenever the body is inflamed — from an infection, arthritis, liver disease or a recent illness — regardless of how much iron is actually available. A high ferritin next to a genuinely low serum iron or transferrin saturation usually reflects that inflammatory pattern, known as anaemia of inflammation, rather than iron overload. Telling the two apart needs a repeat test read alongside transferrin saturation and a marker like CRP, not the ferritin number alone.
What this actually measures
Ferritin measures the concentration of an iron-storage protein circulating in the blood, used as an indirect stand-in for how much iron the body has stored inside cells such as the liver, spleen and bone marrow — but only when nothing else is pushing it independently, since the same protein also rises during inflammation, infection and certain illnesses regardless of iron stores.
| Band | Value | What it depends on |
|---|---|---|
| Typical adult men | roughly 20–500 ng/mL | Assay- and lab-dependent; also rises somewhat with age. |
| Typical adult women (pre-menopause) | roughly 20–200 ng/mL | Lower than men's typical band, largely reflecting menstrual iron losses; also assay-dependent. |
| WHO iron-deficiency threshold, no inflammation present | below 15 µg/L | Set for population surveys and assumes no active infection or inflammation; the same low store can read higher than this if inflammation is present. |
Why this isn’t actually a contradiction
A ferritin result sitting above the normal range next to a serum iron or transferrin saturation sitting below it looks like the two tests are disagreeing with each other. They aren’t. They’re measuring different things, and the gap between them is itself a recognised clinical pattern with a name: anaemia of inflammation, sometimes called anaemia of chronic disease.
What ferritin actually measures
Ferritin is the protein your cells use to store iron, mostly inside the liver, spleen and bone marrow. A small amount leaks into the bloodstream in rough proportion to how full those stores are, which is why a blood ferritin test gets used as a stand-in for total-body iron.
The catch is in that word “rough”. Ferritin is also what’s known as an acute-phase reactant — a protein the liver makes more of whenever the body is dealing with inflammation, infection, active liver disease or certain cancers, entirely apart from how much iron is actually in store. The NIH Office of Dietary Supplements lists this behaviour as a specific limitation of ferritin as an iron-status marker: a high reading taken during or shortly after an inflammatory episode can be a property of the inflammation rather than the iron.
The pattern that shows up on the page
On a standard iron panel, the marker that behaves independently of inflammation is serum iron, and better still, transferrin saturation — the share of iron’s transport protein that is actually carrying iron at the moment of the draw. When ferritin is elevated and one of those two is genuinely low, the report is describing one of several different situations, and telling them apart is the entire reason a full panel gets ordered instead of ferritin alone.
| Ferritin | Serum iron / transferrin saturation | What it usually means | |
|---|---|---|---|
| Iron-deficiency anaemia | Low | Low | Stores are genuinely depleted |
| Anaemia of inflammation | Normal or high | Low | Iron is present but held back by inflammation |
| Iron overload (haemochromatosis) | High | High | Too much iron is actually circulating |
The middle row is the one worth sitting with. Ferritin and transferrin saturation moving in opposite directions is not a lab error — it’s the signature of inflammation interfering with iron traffic, rather than iron actually being scarce or abundant.
Why inflammation does this
The mechanism has a name: hepcidin, a hormone the liver produces in larger amounts during infection and inflammation. Hepcidin’s ordinary job is to keep circulating iron within a safe range by controlling how much is released from storage cells and absorbed from the gut. Under inflammatory conditions, the liver turns that dial up, and the effect is to lock iron inside storage cells and the intestinal lining rather than let it into the bloodstream.
Ferritin, the storage protein, rises because more iron is sitting in store rather than moving. Serum iron falls because that same hormone is throttling its release. Both numbers are telling the truth about what’s happening in the body — they’re just describing two different compartments of it, and the disagreement between them is the actual signal.
A recent infection, a flare of an inflammatory condition such as rheumatoid arthritis or inflammatory bowel disease, active liver disease, chronic kidney disease and some cancers are among the states the same NIH fact sheet names as reasons ferritin can run high independent of iron stores. None of them is confirmed by a ferritin number on its own — the number is a prompt to look at the wider picture, not a diagnosis in itself.
Can you be iron deficient and inflamed at the same time?
Yes, and it’s the scenario responsible for most of the missed diagnoses in this area. An inflammatory illness can lift a ferritin that would otherwise be genuinely low into a “normal”-looking range, effectively masking an underlying iron deficiency. That overlap turns up often in the same chronic conditions already listed — inflammatory bowel disease and chronic kidney disease in particular — where a real iron shortfall and ongoing inflammation are both frequently present at once.
Because ferritin cannot cleanly separate the two on its own in that situation, it needs company. Transferrin saturation, and often a direct inflammation marker such as CRP, read alongside the ferritin, is what actually distinguishes “iron is fine, this is inflammation” from “there’s a real deficiency hiding under the inflammation.”
Reference ranges, and why the exact cut-off shifts
Ferritin’s normal range is wider and less standardised than most bloodwork, because different laboratories run different assays. MedlinePlus lists typical adult ranges as roughly 20–500 ng/mL in men and 20–200 ng/mL in women, while noting that every lab sets its own bounds — the number on your report matters more relative to that specific lab’s printed range than to any figure repeated in an article.
| Typical band | Depends on | |
|---|---|---|
| Adult men | roughly 20–500 ng/mL | Assay, lab, age |
| Adult women (pre-menopause) | roughly 20–200 ng/mL | Assay, lab, menstrual losses |
| WHO deficiency threshold, no inflammation | below 15 µg/L | Assumes no active infection or inflammation |
That WHO threshold is worth understanding on its own terms rather than borrowing casually. It was set for surveying iron deficiency across populations, and the World Health Organization’s own guidance on the measure is explicit that a low ferritin needs adjusting when an inflammation marker is also raised — because inflammation can push a genuinely low ferritin back up toward “normal” too. That’s the opposite direction from the pattern this guide is mainly about, but it’s the same underlying interference: inflammation moving the number away from what it would read if it were only reflecting iron.
When to stop reading and get it checked
Two situations move this out of a reading exercise. A ferritin that is markedly elevated, keeps climbing on repeat tests, and comes with joint pain, unusual fatigue, skin darkening or new-onset diabetes symptoms is the pattern investigated for hereditary haemochromatosis — genuine iron overload rather than inflammation — and it gets confirmed with transferrin saturation and, where indicated, further testing, not with ferritin on its own.
And if the low-iron side of the picture comes with the actual symptoms of anaemia — breathlessness on exertion, a pounding or racing heartbeat, or exhaustion that doesn’t track with how you’ve been sleeping — that also warrants an appointment rather than a repeat test scheduled for next quarter.
Why this is graded “strong,” not “moderate”
Ferritin’s behaviour as an acute-phase reactant is about as settled as clinical chemistry gets. It’s the basis of the World Health Organization’s own global methodology for adjusting iron-deficiency estimates for inflammation, and it’s documented as a specific limitation of the marker by the NIH’s own reference fact sheet on iron. That much isn’t in dispute.
What’s genuinely less certain is the individual case in front of you: whether a specific ferritin number reflects inflammation that’s already resolving, a real but currently masked iron deficiency, or nothing more than last month’s cold. No amount of reading substitutes for the follow-up test that actually answers that, which is why the practical advice below is about getting the right second number, not about interpreting the first one harder.
The practical version
- Repeat the ferritin test once any acute illness or flare has resolved, rather than treating a single reading taken mid-illness as final.
- Ask whether transferrin saturation and a CRP were run alongside it. Those two numbers are what actually separate the rows in the table above — ferritin by itself cannot.
- Don’t decide to start or stop an iron supplement based on a ferritin number alone. The two main patterns above call for opposite responses, and only the fuller panel, read together, tells you which one applies to you.
When to stop reading and see someone
Two situations move this past a reading exercise. A ferritin that keeps climbing on repeat tests alongside joint pain, unusual fatigue, skin darkening or new diabetes symptoms is the pattern investigated for hereditary haemochromatosis, confirmed with transferrin saturation rather than ferritin alone. And breathlessness, a racing heartbeat or exhaustion that doesn't track with your sleep — the actual symptoms of anaemia — warrant an appointment rather than another repeat test.
Questions we get
If my ferritin is high, does that mean I have too much iron?
Not necessarily. Ferritin is what's known as an acute-phase reactant, meaning its blood level rises during inflammation, infection, active liver disease or some cancers, independent of how much iron the body is actually storing or delivering to tissues. A high ferritin reading taken during or shortly after any of those states can reflect the inflammation rather than the iron. The way to tell the difference is to check ferritin alongside a direct measure of circulating iron, such as serum iron or transferrin saturation, and ideally alongside an inflammation marker like CRP.
What is anaemia of inflammation, and how is it different from iron-deficiency anaemia?
Anaemia of inflammation, also called anaemia of chronic disease, is a drop in usable iron and red blood cells driven by ongoing inflammation, infection or chronic illness rather than by too little iron in the diet or blood loss. The lab pattern looks almost the opposite of classic iron-deficiency anaemia: ferritin is normal or high, but the iron available to the bone marrow, reflected in serum iron and transferrin saturation, is low, because the inflammatory response holds iron back inside storage cells instead of releasing it. True iron-deficiency anaemia instead shows a low ferritin alongside the low serum iron, because the stores themselves are genuinely depleted.
Could I have both iron deficiency and inflammation at the same time?
Yes, and this is the scenario that most often confuses a ferritin reading, because an inflammatory illness can push a genuinely low ferritin up into a normal-looking range and hide an underlying iron deficiency. This is common in chronic conditions such as inflammatory bowel disease, chronic kidney disease and rheumatoid arthritis, where both processes can run together. Because ferritin alone cannot reliably separate the two in this situation, clinicians typically add other measurements, such as transferrin saturation or a direct inflammation marker, and interpret the combination rather than the ferritin figure on its own.
Should I repeat the test rather than act on one high ferritin result?
Usually yes, particularly if you had an infection, a flare of an inflammatory condition, or any acute illness around the time of the blood draw, since a temporary rise from that episode can take weeks to settle. Repeating the ferritin test once you are well, and comparing it with serum iron or transferrin saturation at the same time, gives a far more reliable picture than a single number taken during an unrelated illness. A result that stays high after you've recovered is more informative than one taken in the middle of a flare-up.
Where the figures came from
- NIH Office of Dietary Supplements — Iron (Health Professional Fact Sheet) — Ferritin behaves as an acute-phase reactant and can be elevated by infection, inflammation and other illness independent of iron status, which complicates its use as a stand-alone indicator of iron stores
- World Health Organization — Serum ferritin concentrations for the assessment of iron status and iron deficiency in populations — The World Health Organization defines iron deficiency, in the absence of inflammation, as a serum ferritin below 15 µg/L in adults, and its guidance on interpreting ferritin recommends adjusting the reading when inflammation markers are elevated
- MedlinePlus — Ferritin Blood Test — Typical ferritin reference ranges differ between men and women and vary by laboratory and assay
- NHS — Haemochromatosis — Very high ferritin together with elevated transferrin saturation, rather than inflammation, is the pattern investigated for hereditary haemochromatosis
- NHS — Iron deficiency anaemia — Iron-deficiency anaemia is characterised by depleted iron stores, reflected in a low ferritin alongside low circulating iron
Tomas Ottersen
Editor responsible for bloodwork and screening
Tomas edits the bloodwork and screening sections, one marker per entry. His view is that most confusion about test results comes from reference ranges being printed without the context that makes them mean anything: the assay, the population they were derived from, and everything that moves the number besides disease. He is not a clinician and holds no medical qualification, and every entry he edits names the guideline or database its ranges came from.
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