Based on NIH | Does warfarin cause hair loss, and how common is this side effect?

Warfarin can cause hair loss, but it appears to be an uncommon side effect today. Official drug information lists “alopecia” (hair loss) among warfarin’s adverse reactions, and consumer drug monographs also note “loss of hair” as a possible effect. ^{[1] [2]} However, modern clinical experience suggests it is relatively rare, despite older reports that once described high rates. ^[3]

What type of hair loss is linked to warfarin?

• The pattern most often described is diffuse, non‑scarring shedding consistent with telogen effluvium, where more hairs than usual enter the resting (shedding) phase. ^[4] Drug‑related hair loss of this kind typically improves after stopping the triggering medication, though regrowth can take months. ^[4]

How common is it?

• Early case series reported very high rates (42–78%), but these figures are considered out‑of‑date and likely overestimates. ^[3] More recent clinical experience indicates warfarin‑associated alopecia is rare. ^[3] Official labeling acknowledges alopecia but does not provide a precise frequency, reflecting that it is not among the most common side effects. ^[1]

When does it start and how long does it last?

• Hair shedding with medications like warfarin may start weeks to a few months after initiation, consistent with telogen effluvium timing. ^[4] Reports note that alopecia can persist while warfarin is continued, and regrowth may be slow after discontinuation, which can be impractical if anticoagulation must be maintained. ^[3]

Possible mechanisms

• Warfarin alters vitamin K–dependent pathways to reduce blood clotting; while this explains its anticoagulant effect, the exact mechanism for hair loss is not clearly defined. ^[5] Drug‑induced telogen effluvium is thought to involve shifting more hair follicles into the shedding phase rather than direct follicle damage. ^[4]

Distinguishing warfarin from other causes

• Many factors can cause diffuse hair shedding: stress, recent illness, iron deficiency, thyroid problems, hormonal changes, and other medications. ^[4] Hair loss commonly needs a careful review of timing, lab evaluation (for iron and thyroid), and assessment of other drugs to identify the true trigger. ^[4]

Management options

• Continue warfarin if it’s medically necessary and the shedding is mild, while monitoring and addressing other contributors (iron deficiency, thyroid disease). ^[4]
• If hair loss is distressing and clearly linked to warfarin, clinicians may consider switching to another anticoagulant, balancing risks and benefits; note that evidence on recurrence with rechallenge exists, and some alternatives have also reported alopecia in labeling (for example, dabigatran). ^{[3] [6]}
• Gentle hair care, avoiding tight hairstyles and harsh treatments, may help reduce breakage while the underlying issue is addressed. ^[4]
• Regrowth after stopping the trigger usually occurs over several months, reflecting normal hair cycle recovery. ^[4]

Key takeaways

• Warfarin can cause hair loss, but it seems to be uncommon in current practice. ^{[1] [3]}
• The pattern is typically telogen effluvium (diffuse shedding), which is usually reversible. ^[4]
• Older high incidence reports likely overstate the risk; contemporary experience finds it rare. ^[3]
• Always evaluate other causes of hair loss and discuss options with a clinician if shedding is significant. ^[4]

If you’d like help reviewing your medication list and timing of symptoms to see whether warfarin is the likely cause?