Prevention of unconsciousness is related to its underlying cause. For example, avoiding drug use can prevent cases resulting from overdose. Proper treatment of diabetes can prevent many cases due to this disease. Many head injuries can be avoided by following sports safety guidelines for children, adolescents, and adults. Many cases cannot be prevented.
More than half the time, a loss of consciousness is due to simple fainting. Usually, this has no long-term effects. Some people who faint may injure themselves as they fall to the floor.
If the unconsciousness is due to a more serious cause, the long-term effects may be severe. For example, head injuries and strokes can result in permanent brain damage, disability, or death.
A loss of consciousness itself is not contagious. If the loss of consciousness is due to an infection such as meningitis, the infection itself can be contagious.