Alopecia in women is a common problem, and conflicting observational data have failed to determine whether an association exists between alopecia and iron deficiency in women. We therefore utilized an analytical cross-sectional methodology to evaluate whether common types of alopecia in women are associated with decreased tissue iron stores, as measured by serum ferritin. We studied patients with telogen effluvium (n = 30), androgenetic alopecia (n = 52), alopecia areata (n = 17), and alopecia areata totalis/universalis (n = 7). The normal group consisted of 11 subjects without hair loss from the same referral base and source population as those patients with alopecia. We analyzed the data utilizing the unpaired Student's t test assuming unequal variances with an alpha adjustment for multiple comparisons to assess whether the mean ages, ferritin levels, and hemoglobin levels of women without hair loss differed from the means in each alopecia group. The mean age of patients and normals did not differ significantly. We found that the mean ferritin level (ng per ml [95% confidence intervals]) in patients with androgenetic alopecia (37.3 128.4, 46.1]) and alopecia areata (24.9 [17.2, 32.6]) were statistically significantly lower than in normals without hair loss (59.5 [40.8, 78.1]). The mean ferritin levels in patients with telogen effluvium (50.1 [33.9, 66.33]) and alopecia areata totalis/universalis (52.3 [23.1, 81.5]) were not significantly lower than in normals. Our findings have implications regarding therapeutics, clinical trial design, and understanding the triggers for alopecia.