How often do women lactate when they are not pregnant?

Depends of if there: is a reason for it. Possible causes for Galactorrhea include but are not limited to use of birth control pills, tricyclic antidepressants, antipsychotic meds, some sedatives,fennel, anise, fenugreek, some hypertension meds, Cocaine, Opioids,hypothyroidism, prolactinoma, renal dz, pregnancy, testosterone deficiency in men & significant breast stimulation.