An 83-year-old ex-doctor convicted of illegally prescribing more than 2.2 million Oxycodone pills and other opioids — leading to the overdose death of a 26-year-old Staten Island man — will likely die behind bars, after a judge sentenced him to 20 years in a federal prison.

Upper East Side “Oxy doc” Martin Tesher was stone-faced as he learned his fate, following an hour-long hearing in which the dead man’s sister Krystal Benedetto blasted the former physician as a “drug pushing animal,” who ignored her calls to his office when she suspected her late brother Nicholas Benedetto was abusing drugs.

But her messages went ignored, and she said: “Nick fell victim to malpractice, to Tesher’s greed.”

“Patients came to him at their most vulnerable,” Assistant US Attorney Jennifer Sasso told the Brooklyn federal courtroom, which was packed with the ex-doctor’s friends and former patients. “And he did what a common drug dealer would do, he filled them with pills, an astronomical number of pills. Literally millions of pills.”

“This is worse than a common street dealer,” the prosecutor said, urging Brooklyn federal Judge Raymond Dearie to sentence Tesher to 20 years to life in prison.

In his own self-serving statement, Tesher tried to cast blame on his own victim, saying “he was on a great deal of opioids when he came to my office,” and said the prescriptions for Fentanyl he wrote for Benedetto, three days before his 2016 death, were a “lower” dose.

“Why would I jeopardize my life’s work and risk my reputation by doing something that was criminal?” he told the court Tuesday.

Defense attorney Eric Creizman said that being a doctor had given his client’s “life meaning, it gave him purpose,” and that he’d watched Tesher “deteriorate, psychically and emotionally,” since he lost his medical license.

Dearie said he’d tried to find room for leniency, based on Tesher’s age and host of medical conditions, but was still obligated to sentence him to a mandatory minimum of 20 years tied to the patient’s death.

“If this sentence doesn’t deter people, we’re out of business,” Dearie lamented, shaking his head. “A young man died. It should not have happened, it should not have happened,”

“I have a picture of a doctor painted in these letters,” he told a courtroom packed with the ex-doctor’s supporters. “But you obviously know a different Dr. Tesher than I have become acquainted with at trial.”

Tesher was convicted in July 2018 on multiple counts of unlawful distribution of Oxycodone without a legitimate medical purpose as well as a single count of unlawful distribution of Oxycodone and Fentanyl that resulted in a patient’s death. His license was immediately stripped and he went off on both the jury and his own victimized patients outside court.

“I don’t want to be insulting to the jury, but they clearly had no clue,” Tesher told The Post afterwards. “I’ve been in practice for 55 years; these are people who knew nothing about medicine. And calling calling me a murderer because [Benedetto] decided to wildly overdose? Please.”

In the same breath, he called a former patient who’d taken the stand against him a “prick.”

Tesher declined to comment as he left court Tuesday, accompanied by his wife and supporters. He’s been instructed to surrender to the Bureau of Prisons on Aug. 8.

Benedetto said she was pleased with the sentence, after everything her family had been through.

“He’s going to spend his last day in jail, so that sort of evens it out a little,” she stated. “I don’t think he loses a moment of sleep at night.”