Common causes

1. Not enough sleep
   • Short sleep time, irregular schedule, night shifts, jet lag, caring for a child, or insomnia.
   • This is one of the most common causes.
2. Poor-quality sleep
   • Obstructive sleep apnea (OSA): loud snoring, witnessed pauses in breathing, choking/gasping at night, morning headache, dry mouth, and sleepiness despite adequate hours in bed.
   • Restless legs syndrome or periodic limb movements.
   • Pain, reflux, frequent urination, or other conditions repeatedly waking you.
3. Medicines and substances
   • Sedating allergy/cold medicines, sleeping pills, anti-anxiety medicines, opioid pain medicines, some antidepressants/antipsychotics, alcohol, cannabis, and some seizure medicines.
   • Do not stop prescribed medication suddenly. Ask the prescriber or pharmacist to review it.
4. Medical or mental-health conditions
   • Depression, anxiety, thyroid disorders, anemia, diabetes, chronic kidney/liver disease, neurological illness, and chronic pain can contribute.
5. Primary sleep-wake disorders
   • Narcolepsy: sleep attacks, sometimes sudden weakness triggered by laughter or emotion (cataplexy), vivid dream-like experiences on falling asleep/waking, or sleep paralysis.
   • Idiopathic hypersomnia: persistent sleepiness despite long sleep, difficult awakening, “sleep drunkenness.”
   • Circadian rhythm disorder, such as delayed sleep timing or shift-work disorder.

What you can do now

• Aim for a consistent sleep schedule with enough opportunity for sleep, usually 7-9 hours nightly for adults.
• Keep a 1-2 week sleep diary: bedtime, wake time, naps, work shifts, alcohol/caffeine, medicines, and episodes of dozing.
• Avoid alcohol, cannabis, and sedating non-prescription medicines near bedtime unless a clinician advises otherwise.
• Get morning daylight and regular daytime activity. Avoid late-afternoon/evening caffeine.
• If you snore, avoid sleeping on your back if possible and seek assessment rather than relying on sleep aids.
• Do not drive, operate machinery, work at heights, or ride a motorcycle when drowsy. Pull over and arrange another way home if sleepiness occurs while driving.

Medical evaluation and treatment

• Sleep deprivation/circadian issue: schedule correction, sleep hygiene, shift-work planning, and sometimes timed light or specialist-guided treatment.
• Sleep apnea: weight management when relevant, positional measures, oral appliance in selected people, and usually CPAP/PAP. PAP keeps the airway open and can reduce sleepiness, as described by Mayo Clinic’s OSA guidance.
• Medication-related sleepiness: supervised dose, timing, or medication changes.
• Narcolepsy or idiopathic hypersomnia: specialist-directed medicines such as modafinil/armodafinil, other wake-promoting agents, or oxybate-based therapy in selected cases, plus planned naps and regular scheduling. These are not appropriate as a self-treatment before evaluating the underlying cause. A 2026 systematic review of modafinil and a 2024 OSA medication review support selected wake-promoting drugs, but they do not replace treating conditions like untreated sleep apnea (PMID 42468246; PMID 38754208).

Seek urgent medical care now if

• Sleepiness began suddenly with confusion, weakness/numbness on one side, trouble speaking, severe headache, or fainting.
• You are repeatedly falling asleep while driving or at work in a safety-critical role.
• There are serious breathing pauses at night, blue lips, chest pain, or severe shortness of breath.