Ferritin test
Also known as: serum ferritin, iron stores test, ferritin blood test
A blood test that estimates the body's iron stores by measuring ferritin, the protein that holds iron inside cells. It is the best single test for iron deficiency, the commonest cause of anaemia, and it also detects iron overload; because ferritin rises with inflammation, it is often read alongside CRP.
- Kind
- Laboratory test
- Categories
- Vitamins, minerals & nutrition, Blood & haematology, Immunology & inflammation
- Specimen
- Serum
- Method
- Immunoassay
- Terminology
- LOINC 2276-4
- Type
- Blood test
- Sample
- Blood from a vein
- Used for
- Iron deficiency, anaemia, iron overload
- Measures
- Ferritin, the iron-storage protein, as a proxy for body iron stores
- Result
- Numeric with a laboratory reference interval; a guideline cut-off defines depleted stores
Why is it used?
- Anaemia, especially with small red cells (low MCV)
- Tiredness, restless legs, hair loss or brittle nails where iron deficiency is suspected
- Heavy periods, pregnancy, vegetarian or vegan diets, coeliac disease, after gastric surgery
- Suspected haemochromatosis or iron overload from repeated transfusions
- Monitoring iron treatment and, in chronic kidney disease and heart failure, iron status before intravenous iron
What does it measure?
| Component | What it measures | A higher value may be seen in | A lower value may be seen in |
|---|---|---|---|
| Ferritin ferritin Serum ferritin | Iron-storage protein in blood | Inflammation, infection, liver disease, alcohol, iron overload, cancer | Iron deficiency from blood loss, poor intake, malabsorption or pregnancy |
A high or low value can be associated with several different situations; the result is interpreted with other results, symptoms, history and clinical findings.
How is it performed?
A venous blood sample, often with a full blood count and sometimes transferrin saturation.
Specimen. Venous blood (serum)
Do I need to prepare?
None; a recent iron infusion or blood transfusion should be mentioned.
What do the results generally mean?
| Finding | What it may indicate |
|---|---|
| Ferritin below about 30 µg/L in an adult | Iron stores are depleted (iron deficiency), whether or not anaemia is present yet; the cause, often blood loss, is then looked for |
| Normal ferritin with raised CRP and anaemia | Inflammation may be masking iron deficiency; transferrin saturation or a trial of iron helps decide |
| Very high ferritin | Iron overload (haemochromatosis, transfusions) or severe inflammation, liver disease, cancer or a haemophagocytic syndrome |
| Ferritin rising on iron treatment | Stores are being replenished; treatment usually continues for months after haemoglobin normalises |
Guideline thresholds
| Threshold | Value | Unit | Applies to | Country · source |
|---|---|---|---|---|
| Iron deficiency | below 30 | µg/L | Adults; ferritin below this level confirms depleted iron stores. With coexisting inflammation a higher cut-off is used | UK UK |
Clinical decision thresholds come from the named guideline and country; they are not laboratory reference intervals, and they change when guidance changes.
What can affect the result?
- Inflammation and infection raise ferritin regardless of iron stores
- Liver disease, alcohol, obesity and metabolic syndrome
- Recent iron infusion or transfusion
- Time of day and assay differences between laboratories
Medicines. Oral and intravenous iron raise it; regular aspirin or NSAID use can cause the gut blood loss that lowers it; proton pump inhibitors reduce iron absorption.
What can the test not tell you?
- Why iron is low (the source of blood loss must be sought separately)
- Iron status reliably during active inflammation without other tests
- Whether anaemia is due to something other than iron, such as B12 or folate deficiency
Ferritin is an acute-phase protein: any inflammation, infection, liver disease or alcohol excess raises it and can hide a deficiency. It does not show why iron is low; in adults iron deficiency is a reason to look for a source of blood loss, particularly in the gut.
Other tests commonly used with it
Medicines monitored with this test
Each medicine page cites the official document that names this test in its monitoring plan.