Taking 400 mg of modafinil is generally not recommended unless specifically directed by a healthcare provider. The typical prescribed dose is 200 mg per day, usually taken in the morning. While some studies have used higher doses like 400 mg, they showed no significant increase in benefits, but a higher risk of side effects, such as anxiety, insomnia, headache, increased heart rate, and elevated blood pressure. If 200 mg (such as Modvigil 200) isn’t effective for you, consult your doctor rather than adjusting the dose on your own. Taking too much modafinil can lead to overstimulation and interfere with your sleep-wake cycle. Always use modafinil responsibly and under professional supervision to avoid unwanted health risks or dependency.