Does Levothyroxine Cause Hair Loss?
Medically reviewed by Linda Girgis | MD, Girgis Family Medicine on August 20th, 2026.
Levothyroxine rarely causes hair loss as a direct side effect. Hair loss affects less than 1% of patients taking levothyroxine according to clinical studies. However, hair thinning can occur during the first few months of treatment as your thyroid hormone levels adjust. This temporary hair loss typically resolves within 3-6 months once optimal dosing is achieved. More commonly, hair loss results from untreated or undertreated hypothyroidism itself, which disrupts the normal hair growth cycle. If you experience significant hair loss while taking levothyroxine, consult your doctor to evaluate your thyroid levels and rule out other causes like nutritional deficiencies or autoimmune conditions.
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