A bipolar man who was denied his prescription pills for hours by Long Island cops died after officers Tasered him in his jail cell, his family charges in a $50 million lawsuit.

Daniel McDonnell, 40, a carpenter, went into respiratory distress when officers at Suffolk County’s 1st Precinct in West Babylon zapped the mentally ill man twice during a manic episode, the suit claims.

McDonnell — who had a serious heart condition — had been locked up for 18 hours without his meds when he began disrobing and flooding his cell with water, the suit claims.

McDonnell’s mother had earlier tried to get a desk sergeant to accept the crucial medication but was refused, according to the wrongful-death lawsuit filed last week in Brooklyn federal court.

Officers who entered the flooded cell then Tasered McDonnell twice.

“Their own rules absolutely forbid” using the electrically charged weapon on a mentally ill person who is already inside a cell, lawyer Stephen Cirvado said.

The Lindenhurst man had gone peacefully with police on May 5 after a next-door neighbor he regularly battled with called them, claiming McDonnell had violated an order of protection the neighbor had against him.