Cooked or uncooked, hamburger meat left out overnight is not safe to eat. The U.S. Department of Health and Human Services recommends placing cooked food in a refrigerator within two hours of cooking.
Dangerous bacteria can begin forming on food after two hours and can cause serious health issues if consumed. The longer the food product has been left out, the more likely it has become contaminated with bacteria, making it too risky to eat after sitting out all night. Some common bacteria that cause food poisoning are E. coli, salmonella and listeria. These foodborne illnesses can cause brain damage, kidney failure and death in severe cases.