If you're experiencing excessive sleepiness, poor sleep habits are often the cause. It's important to review your routines, schedules, and the environment you're sleeping in so you can spot potential problems and make adjustments.
One of the main causes of sleepiness is insufficient sleep—or less sleep than your mind and body need to function optimally. Most adults need 7-9 hours of sleep per night, and even 30 minutes less can make you drowsy, underproductive, or moody, especially if this "sleep debt" accumulates over time. Avoiding caffeine in the afternoons, winding down in the evening, turning off computers and cell phones (the blue light from these devices may be alerting to the brain), and going to bed at an early and regular time are all important ways to carve out sufficient time and peace of mind for sleep.
What if you diligently craft your bedtime rituals and spend 7-9 hours in bed, but still feel sleepy the next day? In this case, the culprit might be poor sleep quality—or sleep that is interrupted or is not deep and restorative. In some cases, people are aware that they wake up during the night frequently, in which case it may help to practice relaxation, avoid electronic devices, not consume alcohol before bed, and make sure your bedroom is cool, comfortable, and dark. However, if you believe you sleep long enough at night but still feel tired, you could have a sleep disorder like sleep apnea, which drastically reduces the quality of your sleep.
Another reason for excessive sleepiness is a change in schedule, which could be caused by work or school responsibilities. In particular, shift workers, who keep nontraditional hours and often switch schedules, are at high risk for excessive sleepiness. This is because it's difficult to sleep 7-9 hours when those hours are not in line with traditional nightfall, but it's also because when your schedule changes, it takes your body a long time to adjust. Sometimes by the time the adjustment happens, your schedule has shifted yet again. Taking care of your sleep by making sure your bedroom is quiet and dark during your sleep time, exposing yourself to light when you wake up if possible, and trying to keep as regular and consistent a sleep pattern as possible will help. If you've tried to take care of your sleep habits and still find yourself drowsy during the day, it's important to talk to your doctor and ask for a referral to a sleep specialist.