A disturbed man on his way to a medical appointment went berserk in a Midtown doctor’s office, stabbing a man and menacing staffers and patients before he was subdued, police said.

Kane Balser, 25, of Brooklyn, walked into ColumbiaDoctors Midtown on West 51st Street between Fifth and Sixth avenues and suddenly snapped at about 10:30 a.m., cops said.

He allegedly stabbed a 32-year-old man, whose injuries were not life-threatening, and fled.

Balser was caught and taken to Bellevue for a psych exam.