Will you be hurt if you drink one beer while taking xanax (alprazolam)?

No: Unlikely. Xanax (alprazolam) and alcohol can have additive sedative effects but a single beer with a single Xanax (alprazolam) is unlikely to cause serious problems. That said, don't take this combination and drive.

You might: Not nesseserily but you might, alcohol and benzodiazepines are highly not recommended to use together as both are CNS depressants, so technically you can have complications even with lower doses if taken together.