Hypersomnia is excessive sleepiness in conditions of getting physiologically sufficient sleep. Hypersomnia may be related to serious health problems. However, if you keep battling drowsiness, your problem does not need to have a serious organic cause. There is a simple home-grown diagnostic method that can help you eliminate a frequent and less severe cause: a phase shift disorder. Try to free run your sleep for a few weeks. Very often, the phase adjustment will resolve perpetual tiredness! Quite frequently, sleep initiated too early in reference to the circadian sleepiness will last very long and paradoxically result in the feeling of not being refreshed in the morning. If the subjective circadian night period overlaps with the actual waking time, you may experience overwhelming drowsiness, yet you will not be able to fall asleep for longer than 20-30 minutes and you will still wake up unrefreshed. Even buckets of coffee may not help in such circumstances. If you do not notice a significant improvement in the quality of sleep after 1-2 weeks of free running sleep, you may suffer from an underlying health problem that will require a professional consultation. See: Sleep and Hypersomnia at WebMD. A frequent cause of poor quality sleep is Obstructive Sleep Apnea (OSA). OSA is caused by breathing difficulties during sleep.