What is ferritin and why is it tested?
Ferritin is a hollow protein shell that stores iron inside cells — primarily in the liver, bone marrow, and spleen. A small amount circulates in the blood, and this serum ferritin level reflects your total iron stores more accurately than serum iron alone.
Ferritin is ordered to investigate suspected iron deficiency anaemia, to monitor iron stores in people with chronic disease, or to look for iron overload (such as haemochromatosis). It is typically part of a full iron studies panel that may also include serum iron, TIBC (total iron-binding capacity), and transferrin saturation.
Ferritin reference ranges by group
Ranges differ by sex and age. The table below shows approximate ranges from commonly used laboratory standards — your lab may use slightly different values.
| Group | Low (below) | Normal range | High (above) |
|---|---|---|---|
| Adult men | < 12–30 ng/mL | 30–400 ng/mL | > 400 ng/mL |
| Adult women (pre-menopausal) | < 12–20 ng/mL | 20–200 ng/mL | > 200 ng/mL |
| Adult women (post-menopausal) | < 12 ng/mL | 12–263 ng/mL | > 263 ng/mL |
| Children (general) | < 7 ng/mL | 7–140 ng/mL | > 140 ng/mL |
Low ferritin: what does it mean?
A low ferritin is the earliest and most reliable marker of iron depletion — it falls before serum iron, haemoglobin, or MCV become abnormal. It almost always means iron stores are genuinely low.
Common causes of low ferritin
- Inadequate dietary iron — especially in vegetarians, vegans, and those with restricted diets
- Blood loss — heavy menstrual periods, gastrointestinal bleeding (ulcers, polyps, IBD), or frequent blood donation
- Poor absorption — coeliac disease, Crohn's disease, or post-gastric surgery
- Increased demand — pregnancy, rapid growth in adolescents, endurance athletics
Symptoms associated with low ferritin / iron deficiency
Fatigue and reduced exercise tolerance are the most common. Others include pallor, shortness of breath, brain fog, hair loss, brittle nails, restless legs syndrome, and pica (craving non-food items such as ice). Symptoms can precede anaemia — it is possible to be iron depleted without yet having low haemoglobin.
High ferritin: what does it mean?
A high ferritin is less straightforward than a low one. While it can indicate genuine iron overload, it more commonly reflects inflammation, liver disease, or other conditions that cause ferritin to rise independently of iron stores.
Common causes of high ferritin
- Inflammation or infection — ferritin is an acute-phase reactant; any infection, autoimmune condition, or chronic inflammatory disease can raise it substantially
- Liver disease — liver cells release ferritin when damaged (hepatitis, fatty liver, alcohol-related liver disease)
- Haemochromatosis — a genetic condition causing excessive iron absorption; ferritin can reach very high levels (over 1000 ng/mL)
- Metabolic syndrome and obesity — often associated with mildly elevated ferritin without true iron overload
- Excessive iron supplementation — usually from long-term oral or IV iron therapy
- Haemolytic conditions — conditions where red blood cells break down rapidly
- Malignancy — some cancers, particularly lymphomas, can cause very high ferritin
The critical nuance: ferritin and inflammation
This is the most important concept to understand about ferritin testing. Because ferritin rises with inflammation, someone with iron deficiency AND an active inflammatory condition (such as rheumatoid arthritis, IBD, or a recent infection) may have a ferritin result in the "normal" range — masking the true deficiency.
This is sometimes called "anaemia of chronic disease" or "functional iron deficiency." In these cases, doctors look at CRP (C-reactive protein) or ESR alongside ferritin, and may order transferrin saturation (TSAT) and serum iron to get a more complete picture.
Companion tests ordered alongside ferritin
- Serum iron — measures iron circulating in the blood right now
- TIBC / transferrin — rises when iron stores are low (more binding capacity available); falls with inflammation
- Transferrin saturation (TSAT) — serum iron ÷ TIBC × 100; below 20% suggests iron deficiency, above 45–50% suggests overload
- CRP / ESR — markers of inflammation, used to contextualise a ferritin result
- Full blood count (CBC) — haemoglobin, MCV, MCH, and RDW reveal whether iron deficiency has progressed to anaemia
- HFE gene test — ordered if hereditary haemochromatosis is suspected (very high ferritin + high TSAT)
Should you be worried about your ferritin result?
A mildly low ferritin in an otherwise healthy person with clear dietary risk factors is very different from a high ferritin in someone with unexplained symptoms. Context — your symptoms, other blood results, and medical history — determines what action is appropriate. Never start iron supplements based on a single number alone; excess iron can be harmful, and supplementing without identifying the cause of low ferritin can delay diagnosis of serious conditions such as gastrointestinal bleeding.
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