A drug management device includes a first acquisition unit configured to acquire prescription data including data indicative of a drug prescribed to a subject, a second acquisition unit configured to acquire biometric data including data indicative of variations in a physical quantity of a living body of the subject, a first estimation unit configured to estimate, on the basis of the data indicative of variations in the physical quantity, whether or not the subject has taken the drug, and a second estimation unit configured to, in response to an estimation result indicating that the subject has taken the drug, estimate, on the basis of the data indicative of variations in the physical quantity, whether or not an effect of the drug on the subject satisfies an effect estimation criterion, which is predetermined.