Ferritin Blood Test: How to Read Low, Normal and High Ferritin
Ferritin is the body’s iron savings account — until it isn’t. Understand the two clinical roles of ferritin, why the "normal" range can miss real deficiency, and when high ferritin needs urgent attention.
Ferritin below 30 ng/mL confirms iron deficiency — with or without anaemia. Below 100 ng/mL in the presence of inflammation (raised CRP, chronic disease) can still mean deficiency. High ferritin above 500 ng/mL warrants investigation; above 1000 with raised transferrin saturation raises the suspicion of hereditary hemochromatosis.
Ferritin is intracellular iron storage AND an acute-phase reactant. Low ferritin is highly specific for iron deficiency: WHO defines deficiency as < 15 ng/mL (children) or < 30 ng/mL (non-anaemic adults). BSH raises the threshold to < 45 ng/mL when symptoms of iron deficiency are present without inflammation. In inflamed patients (CRP > 5), ferritin < 100 ng/mL should still be interpreted as possibly iron-deficient. High ferritin has three main drivers: inflammation (most common), iron overload (hemochromatosis, transfusion history), and liver injury. Transferrin saturation > 45% is the key finding that separates hemochromatosis from anaemia of inflammation.
- Iron deficiency (no anaemia)
- < 30 ng/mL (< 45 if symptomatic)
- Deficiency with inflammation
- < 100 ng/mL
- Normal
- 30 – 400 ng/mL (assay-dependent)
- High — needs investigation
- > 500 ng/mL
- Hemochromatosis flag
- Ferritin > 1000 + Tsat > 45%
Why ferritin has two clinical personalities
Ferritin is the intracellular protein that stores iron; serum ferritin correlates well with total body iron stores in a healthy person. When body iron falls, ferritin falls first — before haemoglobin drops, before MCV drops. This makes ferritin the earliest and most sensitive marker of iron deficiency.
The complication: ferritin is ALSO an acute-phase reactant. Inflammation, infection, and tissue damage push liver ferritin production up regardless of iron status. Someone with real iron deficiency AND active inflammation can therefore have a "normal" ferritin of 60 — the underlying deficiency is masked. That is why guidelines lift the deficiency threshold when CRP is raised.
Ferritin thresholds by clinical scenario
| Scenario | Ferritin threshold suggesting iron deficiency | Guideline |
|---|---|---|
| Non-anaemic adult, no inflammation | < 30 ng/mL | WHO 2020 |
| Symptomatic adult, no inflammation | < 45 ng/mL | BSH 2021 |
| Adult with active inflammation (CRP > 5) | < 100 ng/mL | BSH 2021 |
| Pregnant, second/third trimester | < 30 ng/mL | BSH pregnancy guideline |
| Older child (5–14 y) | < 15 ng/mL | WHO |
Low ferritin — what to do
Iron deficiency has a cause. In premenopausal women it is usually menstrual loss and low dietary iron. In men and postmenopausal women it is gastrointestinal until proven otherwise (peptic ulcer, coeliac disease, colonic polyps or cancer). Anyone with unexplained iron deficiency and any of the following features needs prompt gastroenterology review: age > 50, weight loss, change in bowel habit, dark stools, or abdominal pain.
Oral iron replacement (elemental iron 65–100 mg on alternate days is now preferred over daily dosing — better absorbed and tolerated) is first line. If oral iron cannot be tolerated, absorption is inadequate (IBD, gastric bypass, coeliac disease), or the deficiency is severe with symptomatic anaemia, an intravenous iron infusion restores stores in one or two visits.
High ferritin — how to think about it
A ferritin between 400 and 1000 in the presence of inflammation, obesity, metabolic syndrome, or non-alcoholic fatty liver is almost always inflammation-driven rather than iron overload. Serum iron is usually low or normal in this pattern, and transferrin saturation is low. This is the "high ferritin, low iron" picture explained in detail in the Elements84 article dedicated to that pattern.
A ferritin above 1000 ng/mL with transferrin saturation above 45% shifts the suspicion strongly toward hereditary hemochromatosis (HFE gene) or secondary iron overload from repeated transfusions. HFE gene testing and hepatology involvement are appropriate. Do not assume "just inflammation" if transferrin saturation is high.
- Ferritin below 30 ng/mL in a man or postmenopausal woman — always assess for GI bleeding.
- Ferritin > 1000 ng/mL with transferrin saturation > 45% — screen for hemochromatosis.
- Ferritin > 400 with bronze skin, joint pain, diabetes, or unexplained liver enzymes — think haemochromatosis.
- Ferritin very high plus persistent fever, weight loss, or night sweats — cancer or macrophage activation syndrome workup.
- Ferritin > 500 with new-onset diabetes and cardiomyopathy — think iron overload.
Ferritin workup decision tree
- 1Ferritin low?Confirm iron deficiency (also check iron studies). Investigate cause: menstrual, gastrointestinal, dietary, malabsorption. Start iron replacement.
- 2Ferritin normal but strongly symptomatic (fatigue, hair loss, restless legs) and CRP elevated?Suspect masked iron deficiency. Recheck ferritin when CRP normalises, or check transferrin saturation and soluble transferrin receptor.
- 3Ferritin high, transferrin saturation LOW or normal?Anaemia of inflammation / metabolic — investigate underlying inflammatory or liver disease.
- 4Ferritin high AND transferrin saturation > 45%?Screen for hereditary hemochromatosis (HFE gene test) and consider hepatology referral.
Related questions people ask
- Can I be iron-deficient with normal haemoglobin?
- What is high ferritin low iron?
- How long does oral iron take to replenish stores?
- When is intravenous iron indicated?
- Does obesity raise ferritin?
- How does menstrual loss affect ferritin?
- Should I test for hemochromatosis?
Frequently asked questions
- Ferritin < 30 ng/mL confirms iron deficiency; < 45 if symptomatic; < 100 if inflamed.
- Iron deficiency has a cause — menstrual, GI, or dietary — and requires investigation.
- High ferritin usually reflects inflammation, not iron overload.
- Transferrin saturation > 45% shifts suspicion to hereditary hemochromatosis.
- IV iron is faster and better absorbed than oral in refractory cases.
- Alternate-day oral iron dosing is now preferred over daily dosing.
References
3 sources- WHOSerum ferritin concentrations for the assessment of iron status
International ferritin thresholds.
who.int
- BSHUK Guidelines on the Management of Iron Deficiency in Adults
UK haematology society guideline.
b-s-h.org.uk
- AASLDHereditary Hemochromatosis
US hepatology society guidance.
aasld.org
Evidence Snapshot
This snapshot shows verified evidence records matched to this article. It is not a diagnosis or personal medical advice.
Ferritin is an acute-phase reactant that can rise with inflammation, infection or acute illness independently of iron stores, so a normal or elevated ferritin drawn during illness does not by itself exclude iron deficiency.
Limitation. The magnitude and duration of the ferritin response to inflammation vary by cause and individual, and no single correction factor applies universally.
A clearly low ferritin is generally considered more specific for iron deficiency than a normal or high ferritin is for iron sufficiency, because ferritin can be raised by inflammation regardless of stored iron.
Limitation. Precise low-ferritin thresholds for iron deficiency vary between guideline bodies and by clinical context (for example, presence of chronic inflammation).
Ferritin thresholds used to identify iron deficiency vary between guideline bodies and by clinical context (such as the presence of chronic inflammation), so a single universal ferritin cut-off is not agreed across all frameworks.
Limitation. Ferritin interpretation may need to be adjusted upward in the presence of chronic inflammation, which no single cut-off captures universally.
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