The duration of modafinil's effect depends on metabolism, dosage, and tolerance. Modafinil acts for 12–15 hours after consumption. Its long duration allows for continuous alertness and cognitive stimulation, which is useful for learning or working on difficult tasks. Within 2 to 4 hours of intake, modafinil may increase alertness, focus, and cognitive performance. Modafinil doesn't replace basic study habits including rest, nutrition, and time management. Modalert 200 may improve cognitive performance and productivity, but it must be used responsibly and as prescribed by a doctor. Overuse of modafinil without medical supervision can cause tolerance, dependence, and side effects. Before using modafinil for studying or cognitive enhancement, visit a doctor.