The appropriate dose and timing depend on the condition being treated. For narcolepsy or obstructive sleep apnoea, modafinil may be taken as a single morning dose or, when prescribed, in divided morning and midday doses. For shift work sleep disorder, the recommended 200mg dose is generally taken approximately one hour before the work shift. Taking modafinil too late in the day may make it more difficult to sleep at night. Always follow the dosage and timing instructions provided by your healthcare professional.