Background Telogen effluvium (TE) is one of the most prevalent causes of diffuse hair loss, because of a defect in hair cycling. Vitamin D plays important role in hair growth, and this is clear in patients with hereditary vitamin D receptor deficiency. Objective This study aimed to evaluate the status of 25-hydroxyl (OH) vitamin D, calcium, and phosphorus in women with chronic idiopathic TE and investigate a probable relationship. Patients and methods A total of 80, Egyptian, nonmenopausal women were recruited for this case–control study. Among them, 40 had chronic idiopathic TE, and 40 were healthy, agematched controls. Serum levels of 25-OH vitamin D, calcium, and phosphorus were measured. Results Serum 25-OH vitamin D levels were significantly decreased in chronic idiopathic TE patients compared with controls (P