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 veteran actor best known as head elf Bernard in 'The Santa Clause' franchise told Page Six he took a long break from smoking marijuana ... but, when he got back into it, it quickly became a daily habit.

Krumholtz says the daily toking took a toll. He developed cannabinoid hyperemesis syndrome ... a rare condition that causes long-term, daily marijuana smokers "repeated and severe bouts of vomiting" according to Cedars-Sinai.

DK admits it's a rare disorder ... but claims cases of it are increasing each year -- and, he believes it's because weed growers are making their product far too strong.

David says, "Essentially, they messed up weed. They made it too strong, and they don’t know why it’s happening. There’s a lot of theories.”

Krumholtz adds he dealt with such severe nausea during a couple of his CHD attacks ... and, he nearly died -- an assertion he claims isn't hyperbolic.

David claims he's got tons of unpaid medical bills from ER visits caused by the disorder ... and no one seems to believe there are dangers when it comes to weed -- 'cause it's the drug that allegedly doesn't kill you.