"I have unpaid emergency room bills up the wazoo. It's really bad. It's really dangerous," David Krumholtz told Page Six.

David Krumholtz claims smoking weed almost killed him -- and, he doesn't mean he thought he was going to die because he got too high ... he says it actually sent him to the hospital.

The “Santa Clause” star told Page Six exclusively that he started using marijuana again after “a long break” and soon became “a daily smoker,” which led him to develop a rare condition ...