Oral minoxidil was originally studied for blood pressure, and the hair growth effects were unintentional. In clinical trials, patients who experienced hypertrichosis ("elongation, thickening, and enhanced pigmentation of body hair") noticed it on the forehead and temples, between the eyebrows, or on the upper part of the cheeks within three to six weeks after beginning treatment. Hair growth on the scalp was observed at a later date.
Similar to topical minoxidil, oral minoxidil takes a few months to produce noticeable results to your crown and hairline. If you stop taking oral minoxidil, new hair growth will stop as well.
Oral minoxidil might not work for everyone or may only partially resolve the concern.