Ferritin

Ferritin is a protein that stores iron in cells; the blood test for serum ferritin reflects the body’s iron stores. It is distinct from serum iron and haemoglobin, which measure circulating iron at a moment in time. A normal haemoglobin can sit alongside a depleted iron store.

For hair loss, ferritin is the single most useful blood test. Low ferritin can prolong telogen effluvium and worsen female pattern hair loss. Restoring it to an adequate level often improves shedding and density.

The reference range issue. Standard labs flag ferritin below 15 to 30 ng/mL as low. Hair specialists typically target above 50 ng/mL for active hair loss; some target above 70. A “normal but on the low side” ferritin of 30 to 40 may be too low for a follicle under stress, even if the lab report shows it as in range.

Ferritin can also be falsely elevated in inflammatory conditions, since it is an acute-phase reactant. In someone with inflammation (infection, autoimmune disease), serum ferritin overestimates true iron stores; transferrin saturation is the cross-check.