Telogen effluvium

Telogen effluvium is diffuse hair shedding that follows a physical stressor. Hair grows in cycles; a shock — surgery, childbirth, illness, a large calorie deficit — pushes an unusually large share of follicles into the resting phase at once. Two to four months later they all let go together. You notice it in the shower drain and in a thinning ponytail, not in bald patches.

It is the hair loss people report on GLP-1 medications, and the timing is the giveaway: it shows up months after starting, typically while weight is coming off fastest. A 2025 retrospective cohort study in the Journal of the American Academy of Dermatology, drawing on the TriNetX database, reported an increased risk of telogen effluvium with tirzepatide compared with other weight-loss medications. A 2025 review in the Journal of Cosmetic Dermatology examined the same association for semaglutide.

The reassuring part is the biology. Telogen effluvium is not scarring — the follicles are intact and dormant, not destroyed. Shedding typically peaks and then resolves over several months once the trigger settles, which for most people means once weight loss slows to a steadier rate. Hair does grow back.

The confusion is attributing it purely to the drug. Rapid weight loss on its own produces telogen effluvium, and so do the nutritional gaps that often accompany eating far less: low protein intake, iron deficiency, low ferritin. Those are checkable and fixable, which is why this is worth a lab panel rather than resignation. Our protein calculator helps set a floor.

Ask a clinician for ferritin, iron studies, thyroid function and vitamin D before assuming the medication is the whole story, and discuss whether slowing the rate of loss would help. Our hair-loss duration guide covers what to expect month by month.