Factual error: The idea that humans only use 10% of their brain is a widely-circulated myth that has been debunked by neurological science many times over.
Revealing mistake: When Lucy is chained and locked up in the room by the Korean drug cartel, she is hit in the stomach by the Korean guy. Drugs start leaking into her stomach and her body, and she starts shaking and going up the wall and ceiling. When she is leaning against the wall and crawling up it, the way the gravity affects the chains and her hair shows that she is actually lying on the floor. (00:25:20)
Other mistake: In the hospital scene wherein Lucy disarms the gunmen and retrieves the briefcase of drugs, she plunges her hands inside a fallen man's abdomen to retrieve the last bag of drugs. Her hands are thus drenched in fresh, bright red blood. Lucy immediately steps to the corridor doors, places her bloody right hand against the door (plainly touching the glass) and pushes it open. But when she pauses and turns away, there are no bloody handprints, fingerprints or blood smears anywhere on the door.
Continuity mistake: After her friend Richard coerces her to go into the hotel with the case to meet Mr. Jang, the man behind the counter who is talking to Mr. Jang asks her name. She says Richard is parking the car and he shows up at the window outside the hotel. Before he is shot, there is red 'blood' already on the window that was not entirely wiped off from previous takes.
Factual error: At the start of the film, cells are shown dividing. As each cell divides, the two new cells separate from each other and move apart from one another. In reality, cells do not move apart after dividing, but remain attached to one another.
Continuity mistake: When Lucy breaks free from the cartel prison room and kills the fellow members we see her eating then removing a bullet she grabs a bag that is half full and begins to add more weapons and items when she lifts the bag from the table for the final time there is less than half a bag.
Continuity mistake: When Lucy is in the chair in the room with the scientists, the mob guy launch a shoulder fired missile into the room, and then the room explode, both Lucy and the scientists are hit, and then Lucy goes back in time. After that when it goes back to the room when the mob boss is about to shoot Lucy's head, the room, Lucy and the scientists are unimpaired.
Revealing mistake: After the drug addict gets shot, one of the henchmen lifts the dead drug addict's leg up and the other leg lifts up with it before the second henchman had a chance to grab it. It looks unrealistic as if it is a prop rather than a real human being dragged.