MAD MEN star JON HAMM is facing a terrifying health scare after a close source says he recently started coughing up blood.

The ENQUIRER has learned that hunk Hamm’s been hiding the fact that he has two large polyps on his vocal cords – and he’s dragged his feet about getting medical treatment for them.

“In the past Jon has been terrified that if he has them removed, his vocal cords could be severely damaged,” said a pal. “Jon has tried to deal with the pain, but over time, he started coughing more and more often, which only aggravated his condition and made his throat feel like it was raw.”

But Hamm, 42, realized he was dealing with something serious when he started coughing up blood.

“He FREAKED out,” said THE source. “He went to see a doctor who told him he needs to have the polyps removed as soon as possible.”

According to the Johns Hopkins Medicine website, vocal cord polyps are “blisters” that are thought to form because of overuse or abuse of the vocal cords. People who use their voices a great deal, like teachers,  lawyers, singers or actors, are more prone to developing them.

Dr. Jerome Spunberg, a radiation oncologist from West Palm Beach, Fla., who has not treated Hamm, tells The ENQUIRER that while most vocal cord polyps are benign, they “can definitely be cancerous.”

“You don’t know without per­forming a biopsy,” Dr. Spunberg explained.

Hamm, who recently finished filming “The Million Dollar Arm,” is planning on having surgery to remove the polyps. So until then, he won’t know if he has cancer or not.

While the multi-award-winning actor appears to be in good spirits about his upcoming procedure, a family insider says that privately, he’s extremely nervous.

“Jon regrets not taking care of this problem before it got to this point,” the insider added. “He’s hoping for the best and preparing for the worst.”