Two mechanisms: anagen effluvium, the fast, dramatic chemotherapy-type shedding of growing hairs, and telogen effluvium, resting hairs dropping together a few months after a trigger, which covers virtually all other drug-related loss, per DermNet NZ.
Common suspects: retinoids, some antidepressants and mood stabilizers, blood thinners, beta-blockers, and hormone changes. The ordinary version is diffuse thinning, usually reversible after stopping or adjusting. Never stop the medicine yourself; bring the timeline to the prescriber, and check thyroid, iron, and stress, which mimic the same pattern.
What to do
Common questions
What medications cause hair loss?
Drug-induced hair loss comes in two flavors, per DermNet NZ's dermatology reference: anagen effluvium, the shedding of actively growing hairs, which is the dramatic chemotherapy version where hair falls within days to weeks of treatment; and telogen effluvium, the shedding of resting hairs, which is the mechanism of virtually all other drug-related shedding and shows up a few months after the trigger, as more hairs than usual shift into the resting phase and drop together. The common-drug list for the subtler version is long: retinoids like isotretinoin, some antidepressants and mood stabilizers, blood thinners, beta-blockers, high-dose vitamin A, some hormone changes like starting or stopping the pill, and gout medications among them. The important truths: the non-chemo version is usually diffuse thinning rather than bald patches, and it is usually reversible, with hair regrowing after the drug is stopped or the body adjusts; and a shed that started two to four months after a new medicine or a change is the classic timeline clue. What to do: do not stop the medicine on your own; bring the timeline to the prescriber, because alternatives within the family often exist; check the other usual suspects, thyroid, iron, and stress, which cause the same pattern; and skip miracle supplements until the cause is sorted.