Ferritin
Also known as: serum ferritin, iron stores
The protein that stores iron inside cells; the small amount in blood mirrors the body's iron reserve. A low ferritin is the most reliable single sign of iron deficiency, but because ferritin is also an acute-phase protein, inflammation can hide a deficiency by pushing it into the normal range.
- Also known as
- serum ferritin, iron stores
- Units
- µg/L (ng/mL)
- Measured by
- Ferritin test, Full blood count, CRP test
What it is and what it does
Most of the body's iron is in haemoglobin, and the rest is held in the liver, spleen and bone marrow wrapped in ferritin. Serum ferritin falls as those stores are drained, before the haemoglobin drops, so it detects iron deficiency at an early stage; a value below about 30 µg/L confirms depleted stores in an adult. Ferritin rises with inflammation, infection, liver disease, cancer and alcohol whether or not iron is present, so in someone with a raised CRP a 'normal' ferritin can still coexist with deficiency, and transferrin saturation or a trial of iron may be needed. Very high ferritin points to iron overload (haemochromatosis, repeated transfusions) or to severe inflammatory states.
Why it may be higher
- Inflammation and infection (acute-phase response), rheumatoid arthritis, inflammatory bowel disease
- Liver disease, alcohol excess, non-alcoholic fatty liver disease
- Haemochromatosis and iron overload from transfusions
- Cancer, especially lymphoma and leukaemia; very high values in adult Still disease and haemophagocytic syndromes
- Metabolic syndrome, obesity
Why it may be lower
- Iron deficiency from blood loss (menstrual, gastrointestinal), poor intake, malabsorption (coeliac disease, gastric surgery), pregnancy and growth
- Hypothyroidism and vitamin C deficiency (small effect)
A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.
What can affect the result
- Any concurrent inflammation raises it independently of iron stores
- Time of day, alcohol, liver disease
- Recent iron infusion or transfusion
Medicines that can change it
Each medicine page lists its effect on this marker under "Effects on tests and results", with the source.