Lindsay Lohan says she was NOT loaded on grandpa's cough medicine -- aka booze, hooch, or liquor -- when she busted her butt in NYC ... telling TMZ flat-out, "I was NOT drinking, nor do I drink!"
LiLo is on the defensive after being photographed going down hard outside the Motor City Bar on Wednesday -- because some people had the audacity to think Lindsay Lohan falling down outside a bar may mean she fell off the wagon.
But that's not the case ... because Lohan tells TMZ, "I was with my brother, sister and friends. I was making a joke. They're trying to make something out of nothing."
Lindsay adds, "Just because I'm out doesn't mean I'm drinking."