A man who believed his mother was poisoning him is suspected of fatally stabbing her inside their Bay Ridge home on Friday night, according to police sources.

The downstairs neighbor of the relatives heard fighting upstairs around 7:30 p.m. — then saw the woman’s 30-year-old son storm out of the two-family home on 93rd Street off Ridge Boulevard, according to cops and sources.

The neighbor went upstairs and discovered the 52-year-old woman suffering from a stab wound to the neck in her bedroom that was covered in blood splatter, and called 911, the sources said.

The woman was pronounced dead at the scene.

Another 911 caller, who identified himself as a friend of the woman’s son, told the dispatcher that the son allegedly stabbed his mother in the neck because he thought she was poisoning him, according to sources.

Police were searching for the dead woman’s son late Friday, sources said.

No arrests have been made.