Ferritin in Blood: Normal Levels, Causes and Significance

Ferritin is more than just an "iron test." It is a storage protein that reflects true iron reserves in the body far more accurately than serum iron itself. Serum iron can be normal even when reserves are completely depleted, while ferritin will reveal the deficiency weeks before anemia develops. This is precisely why ferritin is the first test ordered when iron deficiency is suspected and an essential component of a full iron status panel.

What Ferritin Is and What Role It Plays

Ferritin is an intracellular iron-storage protein: each ferritin molecule can hold up to 4,500 iron atoms in a non-toxic, biologically available form. It is present in virtually all cells but is most concentrated in hepatocytes, bone marrow macrophages, and reticuloendothelial cells.

In serum, ferritin circulates in small amounts — it "leaks" from cells in proportion to their iron content. This is why serum ferritin correlates with total body iron stores: 1 µg/L of serum ferritin ≈ 8–10 mg of stored iron.

Functions of ferritin:

• Iron storage — protects cells from toxic free iron (Fe²⁺), which generates reactive oxygen species via the Fenton reaction
• Erythropoiesis regulation — iron deficiency impairs hemoglobin synthesis and red cell production
• Acute phase protein — during inflammation, ferritin synthesis rises sharply regardless of iron stores; this is critically important for interpreting elevated results

A detailed clinical guide to interpreting ferritin across different clinical situations is available in ferritin: how to read your blood test.

Normal Ferritin Levels

Reference values depend substantially on sex and age. Women have significantly lower iron stores due to menstrual losses.

Group	Normal ferritin (µg/L / ng/mL)
Newborns	25–200
Infants 1–5 months	50–200
Children 6 months – 15 years	7–140
Men 18–45 years	20–250
Men 45–65 years	20–300
Women 18–45 years (premenopausal)	10–120
Women postmenopause	20–200
Pregnant (1st trimester)	10–90
Pregnant (3rd trimester)	5–50

Clinically relevant thresholds:

Ferritin level (µg/L)	Interpretation
< 12–15	Absolute iron deficiency
12–30	Depleted stores (pre-latent deficiency)
30–100	Normal (lower range)
100–300	Normal (mid to upper range)
> 300 (F) / > 400 (M)	Elevated — possible excess or inflammation
> 1000	Significant elevation — active diagnostic workup required

Key nuance: in patients with chronic inflammatory disease, a "normal" ferritin of 50–100 µg/L may conceal genuine iron deficiency — inflammation raises ferritin independently of iron stores. In the presence of active inflammation, ferritin < 30–50 µg/L is the diagnostically meaningful threshold for iron deficiency.

How to Prepare for a Ferritin Blood Test

Ferritin is a relatively stable marker, but several factors influence the result.

• Fasting for at least 8 hours is recommended — food has little direct effect on ferritin, but fasting is required when the full iron panel (including serum iron) is ordered simultaneously
• Stop iron supplements 5–7 days before the test — iron-containing medications transiently elevate ferritin
• Acute illness, infection, or active inflammation significantly raise ferritin as an acute phase protein — defer testing 6–8 weeks after resolution or interpret alongside CRP
• For serial monitoring: same laboratory each time
• Blood transfusion in the preceding 2–4 weeks distorts the result

Ferritin is always interpreted alongside other iron status markers: serum iron, TIBC (transferrin), transferrin saturation, and when needed — soluble transferrin receptor (sTfR).

Causes of Low Ferritin

Low ferritin is the most reliable marker of depleted iron stores. There are virtually no other causes of sub-normal ferritin.

Cause	Mechanism	Characteristic features
Chronic blood loss (menstruation, GI bleeding)	Iron losses exceed intake	Most common cause in women
Inadequate dietary iron intake	Insufficient substrate for storage synthesis	Vegetarian and vegan diets; restrictive eating
Impaired iron absorption	Reduced duodenal absorption	Celiac disease, Crohn's disease, gastrectomy
Pregnancy and lactation	Increased iron demand	Physiological fall in 3rd trimester
Chronic iron deficiency anemia	Sustained deficiency with inadequate treatment	Low hemoglobin + low ferritin
Intense physical training	"Footstrike" hemolysis, myoglobinuria, sweat losses	Endurance athletes
Regular blood donation	Direct iron loss with each donation	Frequent donors

In iron deficiency anemia, ferritin falls first — well before hemoglobin drops. The sequence of iron depletion: ferritin ↓ → transferrin saturation ↓ → MCHC ↓ → hemoglobin ↓. Ferritin is the only marker that catches iron deficiency before anemia develops.

Symptoms of iron depletion without anemia ("pre-latent deficiency"): chronic fatigue, difficulty concentrating, hair loss, restless legs syndrome, reduced exercise capacity. Many patients live for years with ferritin of 8–15 µg/L and normal hemoglobin, unable to explain why they feel chronically unwell.

Causes of High Ferritin (Hyperferritinemia)

Elevated ferritin is one of the most common "puzzling" biochemical findings: it can reflect iron accumulation, systemic inflammation, or serious disease.

Cause	Ferritin level	Characteristic features
Inflammation and infection	Moderate (100–500 µg/L)	Elevated CRP; acute illness signs
Non-alcoholic fatty liver disease	Moderate–significant	Obesity; elevated ALT; insulin resistance
Alcoholic liver disease	Moderate–significant	AST/ALT > 2; elevated GGT
Hereditary hemochromatosis	Significant (> 500–1000 µg/L)	Transferrin saturation > 45%; HFE mutation
Malignancies	Variable, often > 1000 µg/L	Often unrelated to actual iron stores
Hemophagocytic lymphohistiocytosis (HLH)	Very high (> 10,000 µg/L)	Pancytopenia; fever; splenomegaly
Multiple blood transfusions	Significant	Transfusional iron overload
Chronic kidney disease	Moderate	Parallel erythropoiesis impairment
Metabolic syndrome	Mild–moderate	Obesity; high TG; hypertension
Hyperthyroidism	Mild	Falls with TSH normalization

Hereditary hemochromatosis is the most important cause of significantly elevated ferritin that must not be missed. Iron accumulation in the liver, pancreas, heart, and joints — if untreated — leads to cirrhosis, diabetes, cardiomyopathy, and arthropathy. Screening marker: transferrin saturation > 45% combined with ferritin > 300–400 µg/L. Confirmed by genetic testing for the C282Y mutation in the HFE gene.

HLH (hemophagocytic lymphohistiocytosis) — a life-threatening condition: ferritin rises to 10,000–100,000 µg/L and is a diagnostic criterion. Every clinician should recognize this threshold.

Ferritin as an Iron Marker vs. an Inflammation Marker

The central diagnostic challenge with ferritin is that it simultaneously reflects two entirely different things: iron stores and the inflammatory response. This makes interpretation non-trivial.

In health: ferritin reflects iron stores — low = deficiency; high = excess.

In inflammation, infection, or malignancy: ferritin synthesis in the liver and macrophages is sharply upregulated as an acute phase response — independent of actual iron stores. This masks true iron deficiency:

Classic diagnostic trap: a patient with rheumatoid arthritis has ferritin of 80 µg/L — seemingly normal. But if CRP is 40 mg/L, the ferritin in the absence of inflammation would be around 15–20 µg/L — indicating significant iron deficiency. This is why ferritin must always be interpreted alongside CRP and the soluble transferrin receptor (sTfR) — the latter rises in iron deficiency and does not respond to inflammation.

Practical decision framework:

• Low ferritin + normal CRP → absolute iron deficiency; treat
• Normal/high ferritin + high CRP → possible occult deficiency; check sTfR
• High ferritin + normal CRP → iron overload or storage disease

When Ferritin Abnormalities Require Medical Attention

Scheduled visit to a doctor when:

• Ferritin < 20–30 µg/L — especially in women and with symptoms (fatigue, hair loss, exercise intolerance) — prescribe iron supplementation and investigate the cause
• Ferritin > 300 µg/L (women) or > 400 µg/L (men) without an obvious inflammatory condition — rule out hemochromatosis and liver disease
• Ferritin > 1000 µg/L — regardless of symptoms — active diagnostic workup required

Seek urgent care when:

• Ferritin > 5000–10,000 µg/L — rule out HLH and hematological malignancies
• Low ferritin combined with severe anemia (hemoglobin < 90 g/L)
• Rapidly rising ferritin in a patient with known disease — possible decompensation or malignant transformation

This article is for informational purposes only and does not replace professional medical advice. Consult a GP or hematologist if your ferritin level is outside the normal range.