Lindsay Lohan Run Down ... By a Bike

Didn't your momma tell you to look both ways before crossing the street?

Sources tell TMZ Lindsay Lohan was out in NYC last night with gal pal Samantha Ronson, and as they were leaving, Lilo got hit by someone on a bike.

We're told her driver took her to Beth Israel Hospital in Midtown Manhattan and she checked herself out at 4:00 AM.