Researchers gathered 36 published studies comparing iron stores in women with non-scarring hair loss against women without it, and pooled the numbers into one analysis. Ferritin is the blood marker that reflects how much iron the body has in storage. Altogether the studies covered 10,029 women, 6,641 of them with some form of hair loss including telogen effluvium, female pattern hair loss and alopecia areata.

Pooled together, women with hair loss had ferritin levels averaging about 18.5 units lower than women without it, and that gap held up across the analysis. Then comes the part that usually gets left out. The same authors report that outright iron deficiency was no more common in the women with hair loss than in the general population, and neither was iron deficiency anemia. Their own summary sentence is careful: women who complain of hair loss may benefit from higher ferritin levels. Worth knowing about the analysis itself, the results varied enormously from study to study, which makes the pooled number a direction rather than a precise target. Every included study was observational, so nothing here tests whether raising ferritin changes anything. Most came from referral centers and hospitals rather than the general population. And the literature search stopped in 2019.

Here's the study: Treister-Goltzman Y, Yarza S, Peleg R. Iron Deficiency and Nonscarring Alopecia in Women: Systematic Review and Meta-Analysis. Skin Appendage Disorders, 2022;8(2):83-92. Read it here

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