An employee at an Upper East Side juice shop was repeatedly stabbed and left gravely wounded during a clash with a woman late Wednesday, cops said. 

The 39-year-old worker got into a fight with the suspect inside Juice Island on Third Avenue near East 61st Street around 8:30 p.m. Wednesday, authorities said. 

The woman then picked up a knife from the counter and stabbed the man in the head, neck, back and hands, authorities said. 

The assailant fled on foot, heading north on East 61st Street, cops said. 

The victim was rushed to Weill Cornell Medical Center, where he was listed in critical condition, cops said. 

Business owner Sam Alherish – who rushed to the scene after getting a call about the violent crime – told The Post a short time later that he hadn’t been able to speak with his employee.

“He’s in the hospital,” Alherish said. “He lost a lot of blood. I don’t know if he’s conscious or not.” 

Alherish said the incident marks the third assault that has taken place inside his business since it opened less than seven years ago – and this might be the last straw. 

“I’m telling you, now I’m thinking about just closing the business,” he said. “I don’t want to take the chance anymore.”

The nature of the fight between the victim and the attacker was unknown by Thursday afternoon and no arrests had been made.

Authorities released a photo of the suspect and described her as between 20 and 30 years old, blonde, with a medium to dark complexion and standing around 5-foot-6. 

She was last seen wearing a pink or purple hooded sweatshirt, black pants and black and white sneakers.