Does low ferritin cause hair loss, particularly telogen effluvium?

Iron is an essential cofactor for the physiological processes governing the hair growth cycle. Low serum ferritin levels—the primary marker of stored iron—are strongly associated with hair loss, particularly telogen effluvium (TE), where hair prematurely shifts into the shedding phase.

Clinical evidence

• Correlation with shedding: Research consistently identifies lower ferritin levels in women experiencing hair loss compared to healthy controls. In studies of women with TE, up to 86% exhibit ferritin levels below 40 ng/mL. Furthermore, an inverse correlation exists between ferritin concentration and shedding severity (r = -0.53, p < 0.0001).
• Thresholds for health: While standard laboratory ranges for ferritin are broad, evidence suggests a "critical threshold" for hair health typically between 40 and 70 ng/mL. Patients who achieve levels ≥50 ng/mL through supplementation report significantly higher satisfaction and improved hair density compared to those with lower levels.
• Treatment response: Increasing iron stores has been shown to improve hair coverage and density, reinforcing the causal link between iron status and follicular maintenance.

Mechanistic explanations

• DNA synthesis: Iron is a necessary cofactor for ribonucleotide reductase (RNR), the rate-limiting enzyme in DNA synthesis, and for the stability of DNA polymerase δ via iron-sulfur clusters.
• Cellular proliferation: The anagen (growth) phase of the hair cycle requires rapid mitotic activity in matrix keratinocytes. When iron is deficient, impaired DNA replication and potential disruptions in mitochondrial ATP production hinder this cellular division.
• Cycling disruption: This metabolic stress triggers a premature transition from the active anagen phase to the telogen (resting) phase, leading to the synchronized shedding characteristic of telogen effluvium.

Bottom line

Low ferritin is a scientifically validated risk factor for telogen effluvium. Maintaining adequate iron stores is essential for the DNA synthesis and rapid cell division required for healthy hair follicle cycling and growth.