Kevin Costner is shedding light on his difficult time filming Hidden Figures.

"I've never worked drunk on a set. I've never worked high on a set, but I was on morphine the last two weeks that I worked on [Hidden Figures],” he revealed in a new PEOPLE video. “I had kidney stones and I worked 10 days under an [IV] drip. I don't even know how.”

The actor, who played Al Harrison, the fictional director of NASA’s Space Task Group, in the 2016 drama, revealed that he only felt normal for “about three days” of shooting before his health took a sudden turn for the worse.

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“I didn’t miss a day of work — I’ve never missed a day of work — and then when I thought I was gonna be off it, a second kidney stone came, which I never had, and I was right back on it,” he recalled. “So I sat in my trailer with a morphine drip in my arm.”

His IV treatment also left him with bruising that affected his performance in the film. “I eventually had to have my sleeves down in the movie as opposed to rolled up because of that,” he said. "I wanted to cry, but there was everybody watching, so I didn't."

Based on Margot Lee Shetterly’s 2006 nonfiction book of the same name, Hidden Figures follows the real-life story of three Black female mathematicians working at NASA at the height of the Space Race. The film starred Taraji P. Henson, Octavia Spencer, and Janelle Monáe as its core trio, with Costner, Kirsten Dunst, and Jim Parsons playing their NASA coworkers.

In the years since the film’s release, Costner has continued to dedicate himself to projects like his new Western epic Horizon: An American Saga, which he co-wrote, directed, and largely funded on his own. However, he recently told Entertainment Weekly that he’s not fretting too much over how the film performs at the box office.

"I've lived with movies and what happens to them on their opening weekend," he said. "If we put so much pressure on that, we're bound to be disappointed. I'm really happy that Horizon looks like what it's supposed to look like, and that's the way it'll look the rest of its life. And that's really important to me in this process."