Iron deficiency is the most common nutritional cause of hair loss globally, particularly in women, and it is often overlooked because standard blood tests may not reveal it. Understanding the specific relationship between iron levels and hair helps patients get the right tests and interpret the results correctly.
Iron is required for the proliferation of hair matrix cells — the cells that produce the hair shaft within the follicle. Insufficient iron impairs this process, causing hair to grow more slowly and enter the telogen (shedding) phase prematurely. The result is diffuse hair thinning and increased shedding, often noticed in the shower or when brushing.
The critical distinction is between serum iron and ferritin. Ferritin is the stored form of iron and is a more sensitive indicator of depletion than serum iron levels. A patient can have a normal serum iron level but depleted ferritin stores — and it is the ferritin level that correlates most closely with hair loss. Studies have shown that ferritin levels below 30 to 40 ng/mL are associated with increased hair shedding, even in patients who are not clinically anaemic.
Treatment is straightforward — iron supplementation, ideally taken with vitamin C to enhance absorption, and with attention to dietary sources. Results take three to six months to manifest as visible improvement in hair density. The timeline reflects the length of the hair growth cycle, not the speed of iron replenishment.
If you are losing hair and have not had a ferritin level checked, this should be one of the first investigations. The test is inexpensive, widely available, and frequently reveals a correctable cause that other treatments cannot address.
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