Michael Douglas reveals in his new memoir, “One Helluva Ride,” that he lost 40 pounds “that I didn’t really have to lose” during his brutal battle with stage four throat cancer.

The “Fatal Attraction” star writes that he underwent seven weeks of radiation and chemo, which he compares to “the seven circles of hell,” after receiving his diagnosis in August 2010.

“At first, the pain was bad but manageable, but by the third week I was in real trouble,” he recalls, adding that he was “sallow and gaunt” after four weeks of treatment.

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Douglas says his cancer also brought on “hard moments” for his wife, Catherine Zeta-Jones, and their two children, son Dylan, now 26, and daughter Carys, now 23, who saw headlines claiming that their dad was close to death.

“The kids were too young to understand how these magazines operate, so it was traumatizing for them,” he writes.

The Oscar winner explains that he was determined to “maintain normalcy” with his kids, including taking Carys to school every day, which left him “so exhausted” that he’d have to lie down on the couch for the rest of the day.

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“That couch had become my chair, my desk, my table, my bed, my life raft on a sea of complete exhaustion,” Douglas writes, adding that most of his visitors would find him in the same spot.

Douglas also remembers how his late father, actor Kirk Douglas, was “stoic” during his cancer battle, but still supported him by dressing up as a clown one day at the hospital on Halloween.

“In that moment it was the best gift he could have given me,” Douglas writes.

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After a period of recovery from his seven-week treatment, the “Basic Instinct” actor says he was shocked to learn from his doctors that his cancer was in remission.

“I broke down crying,” Douglas recalls of the life-changing moment. “To say cancer humbled me would be an understatement. It made me more thankful for everything in my life.”

Douglas also writes that following his health crisis, Zeta-Jones, now 57, said it was like “watching a wilted flower come back to life.”

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The father of three also admits that having cancer gave him freedom.

“It’s difficult to talk about, but it felt like a rebirth,” he writes. “My priorities changed. Cancer showed me what family is. It made feel a love that I never knew really existed.”

“I saw everything a little bit clearer, and a little bit brighter, and became far more conscious of how I spent my time,” Douglas adds.

“One Helluva Ride” is out now.