A Queens couple says an animal hospital killed their beloved cat by accidentally prescribing her medication for an animal weighing six kilograms — or more than twice her actual weight of six pounds.

The Blue Pearl veterinary clinic then added insult to injury by demanding that the owners of long-haired tortoise-shell Camry still pay for the horribly botched treatment, according to the couple’s lawsuit.

“We feel that it’s absolutely immoral that Blue Pearl would charge us many thousands of dollars for the privilege of having our cat killed,” owner Matthew Ritter fumed to The Post.

Ritter and his wife, Louise, are now suing Blue Pearl for $290,000, which includes $250,000 for their mental anguish — and, in a rare legal move, $10,000 for Camry’s “suffering,” court papers show.

The 45-year-old drumming instructor said his and his wife’s ordeal began when he brought their 17-year-old kitty to Blue Pearl’s Forest Hills clinic in March with a kidney disorder.

A vet there said the kitty was treatable, but when Ritter came to visit her the next day, Camry was face-down in a litter box, “quivering and unresponsive,” according to the couple’s suit, filed in Manhattan Supreme Court, where Blue Pearl is based.

That’s when the clinic discovered its fatal error, the court papers state.

It had given Camry a dosage of medicine based on 6 kilograms, or more than 13 pounds, which amounted to 220 percent of what she should have received, according to the suit.

“They admitted that they did this, but there was never really any compassionate apology,” Ritter said.

Camry was placed in an oxygen cage, but she couldn’t be saved. She died on April 15.

The lawsuit seeks a refund of $15,000 for the Ritters’ vet bills, $5,000 for the value of Camry, $10,000 for her “unnecessary pain and suffering,” another $10,000 for the wages the husband and wife say they lost while dealing with the fiasco and $250,000 for their mental anguish.

The couple’s lawyer, Richard Bruce Rosenthal, who specializes in pet cases, said that while seeking money for an animal’s personal suffering is rare, it is appropriate in this case.

“Defendants were aware that Camry was a conscious, loving and sentient being who experienced pain, physical suffering and emotional joy and emotional suffering in a manner similar to that of humans,” his clients’ suit says.

“Therefore, they knew that the suffering and death which they would cause Camry, by their reckless, grossly negligent and intentional wrongdoing would also cause emotional distress to’’ the Ritters.

Blue Pearl told The Post in a statement, “As an organization of pet lovers, we care deeply about every pet we treat. While we have not been served with this complaint, we are still in communication with the Ritter family and hope to address their concerns.”

This is not the first time Blue Pearl has faced a lawsuit over a pet’s death.

Just last week, the animal hospital settled a case with Manhattan lawyer Andrew Sachs, who claimed that the Blue Pearl clinic on West 55th Street gave his Shih Tzu/toy-poodle mix Mimosa a nearly lethal cocktail of prescription drugs.

Details of that deal are not public.