Eagles rocker Glenn Frey suffered from debilitating rheumatoid arthritis for years — and died partly because of the pills he took for it, his manager said Tuesday.

“He died from complications of ulcer and colitis after being treated with drugs for his rheumatoid arthritis, which he had for over 15 years,’’ the singer’s manager, Irving Azoff, told the Web site The Wrap.

“The colitis and pneumonia were side effects from all the meds,” Azoff said.

The manager, recalling Frey’s struggle with the crippling joint condition, added, “One day, [Frey’s] knees would hurt, his hands hurt.’’ The illness “moves from joint to joint,’’ he said.

Frey, who lived with his wife, Cindy, in Tribeca, died Monday at Columbia University Medical Center, part of New York-Presbyterian, in Washington Heights. He was 67.

His health battles over the years led him to fight to stay in shape to keep things under control, said rocker pal Bob Seger.

“[He was] a workout warrior from his 30s to his 60s,” Seger, 70, told the Detroit Free Press.

Frey’s final decline began roughly a month after his last performance with the Eagles in Bossier City, La., on July 29, said his brother, Alan Frey, to The Post.

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