What does it measure?
Ferritin is a protein that stores iron inside cells. The amount measured in blood helps estimate your iron reserves. It is different from serum iron, which measures iron circulating at that moment, and can help identify depleted stores before hemoglobin falls. [1]
Before the test
- Sample
- Blood.
- Preparation
- Your clinician may request fasting. Confirm the laboratory’s instructions, especially when other iron tests are included.
- What to mention
- Recent illness, heavy bleeding and iron treatment are useful context for the result.
What can the result mean?
A low ferritin usually points toward reduced iron stores. A high ferritin is more complicated: inflammation, liver conditions, recent illness, or iron overload can raise it. Because it responds to inflammation, a usual or high ferritin does not always exclude iron deficiency. [1]
When is it useful, and how is it read?
For fatigue or suspected iron loss, interpret ferritin with the history of bleeding, intake, and absorption. Low ferritin supports depleted stores; normal or high ferritin during inflammation can be less reassuring. Hemoglobin and transferrin saturation may help clarify the pattern. [1] [7] [8]
Reading the results together
| Marker | What it adds |
|---|---|
| Ferritin | A clue to iron reserves, also affected by inflammation. |
| Iron | Iron circulating in the blood sample. |
| Hemoglobin | The oxygen-carrying protein in red cells. |
These results can change at different times. A ferritin result needs the iron pattern and any inflammation beside it. [1] [3] [4]
What can affect it?
The result is most useful with your CBC, transferrin saturation, symptoms, and sometimes CRP. Heavy periods, blood donation, gastrointestinal blood loss, and reduced absorption may explain deficiency. Supplements and recent treatment also matter when comparing results. [1]
Iron stores can fall before hemoglobin does
Iron deficiency develops in stages. Ferritin may fall while hemoglobin and red cell size still look normal, so a normal CBC does not always mean iron stores are adequate. [7] [8]
Questions you might have
Is ferritin the same as serum iron?
No. Ferritin helps assess stored iron; serum iron reflects iron circulating at that moment. [3]
Does high ferritin always mean too much iron?
No. Inflammation and liver problems can raise it too. Other iron results and the health context help separate the possibilities. [1]
What comes next?
If stores are low, ask why as well as how to replace iron. If ferritin is high, your clinician can review the iron profile and liver or inflammation context before labeling it iron overload. Do not start iron or arrange blood removal from this number alone; the cause determines the appropriate step. [1]
Does this ferritin reflect my iron stores, inflammation, or a combination of the two?
The reference interval and units on your report are part of understanding your result. Understand units, reference intervals, and treatment targets.
Sources & references
Medical references & original research
- MedlinePlus — Ferritin blood test
- MedlinePlus — Iron tests
- MedlinePlus — Hemoglobin test
- World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. Evidence and recommendations. 2020.
- RCSB Protein Data Bank. PDB-101 Molecule of the Month: Ferritin and Transferrin. November 2002.
Further reading
Books we consulted
References that informed our explanations of the test and its context.
- Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic and Laboratory Test Reference. 14th ed. Elsevier; 2019.
- Provan D, editor. Oxford Handbook of Clinical and Laboratory Investigation. 4th ed. Oxford University Press; 2018.
Practical-section sources accessed: .
For general health education. Interpreting your result and deciding on tests or treatment requires your health context and a qualified clinician.
