Sleep guides
Clear, sourced answers to common sleep questions, fact-checked against their sources.
Alcohol and sleep
Does Alcohol Help You Sleep? What a Nightcap Really Does
Alcohol helps you fall asleep faster, then breaks up the second half of the night and cuts REM sleep. Here is how a nightcap changes your sleep, drink by drink.
GuideWhy Do I Wake Up at 3 a.m. After Drinking?
Waking at 3 or 4 a.m. after drinking is a rebound: as alcohol wears off, sleep turns light, your heart races and your bladder fills. Here is what helps.
Body clock and light
What's the Best Room Temperature for Sleep?
For most adults, a bedroom of about 60 to 68°F (16 to 20°C) works best. Why a cool room helps, how humidity and bedding change it, and what to do on hot nights.
GuideDoes Blue Light Really Affect Sleep? What the Studies Show
Yes, but brightness and timing matter more than color alone. What studies show about screens, night mode, warm bulbs and sleeping with the lights on.
GuideHow Long Should You Get Morning Sunlight?
No study has set a dose, but 15 to 30 minutes outdoors soon after waking is a sensible practical start, with more on gray days. Here is what the research says.
GuideWhy Do I Get Sleepy in the Afternoon (Around 2 p.m.)?
The 2 p.m. slump comes mostly from your body clock and rising sleep pressure, not just lunch. Why it happens, why short nights make it worse, and what helps.
Caffeine and sleep
How Long Before Bed Should You Stop Drinking Coffee?
Research suggests finishing a regular coffee about 9 hours before bed, and strong caffeine drinks up to 13 hours before. Why even 6 hours may not be enough.
GuideWhy Does Coffee Make Me Sleepy?
Coffee can leave you tired because caffeine only masks sleepiness, daily use blunts its effect, and short sleep wins out. Five reasons, and what helps.
Chronotype
Can a Night Owl Become a Morning Person?
Partly. Genes set your starting point, but light and a fixed routine shifted night owls about two hours earlier in three weeks. What works and what slips back.
GuideIs It Bad to Go to Bed at 2 a.m. Every Night?
A 2 a.m. bedtime isn't harmful in itself if you still sleep 7+ hours at steady times. Trouble starts with early alarms, drifting schedules and missed daylight.
GuideSocial Jet Lag: Why Weekend Lie-Ins Make Monday Feel Like a Flight
Social jet lag is the gap between your sleep timing on workdays and free days. How it is measured, how common it is, what it is linked to and how to shrink it.
Falling asleep and sleep efficiency
How Long Should It Take to Fall Asleep?
Most healthy adults fall asleep in about 10 to 20 minutes. Here is what counts as normal sleep latency, when slow sleep onset is a concern, and what helps.
GuideShould You Get Out of Bed If You Can't Sleep?
Yes: if sleep has not come after about 20 minutes, get up, do something calm in dim light and return when sleepy. Here is why it works and how to do it well.
GuideWhy Do I Fall Asleep So Fast? Is Falling Asleep Instantly Normal?
Dropping off within a few minutes is often a sign you are short on sleep, not a talent. Learn what counts as too fast, why it happens and when to see a doctor.
GuideWhy Do I Sleep Better on the Couch Than in My Bed?
If you doze off easily on the sofa but lie awake in bed, your bed may have become a cue for being awake. Here is why that happens and how to retrain it.
GuideWhy Do I Wake Up at 3 a.m. Every Night?
Brief waking in the night is normal; sleep gets lighter in the early hours. Here is why 3 or 4 a.m. is so common, what triggers it and how to drift off again.
Jet lag
How Long Does Jet Lag Last?
Jet lag usually lasts about a day per time zone crossed, a little less flying west. See typical recovery times for US to UK, Europe, Japan and 12-hour trips.
GuideIs Jet Lag Worse Flying East or West?
Flying east is usually harder, because your body clock runs slightly longer than 24 hours and finds it easier to stay up late than go to bed early.
Naps
What Is the Best Time to Take a Nap?
The best time to nap is early afternoon, in the natural post-lunch dip and at least 8 hours before bed. Why late naps backfire, and who should skip them.
GuideThe Caffeine Nap: Does Coffee Before a Nap Really Work?
A caffeine nap means drinking coffee, then napping 15 to 20 minutes so the caffeine kicks in as you wake. What the studies found and when to skip it.
GuideHow Long Should a Nap Be? 10, 20, 30 or 90 Minutes
For most adults, a nap of 10 to 20 minutes gives the quickest lift with the least grogginess. Here is what 5, 10, 20, 30, 60 and 90-minute naps each do.
GuideWhy Do I Feel Worse After a Nap?
Feeling groggy or awful after a nap usually means you woke from deep sleep. Why it happens, why sleep debt makes it worse, and how to clear the fog faster.
Shift work
How to Sleep During the Day After a Night Shift
Go to bed soon after you get home, keep morning light out of your eyes, and make the room dark, cool and quiet. A practical guide to daytime sleep after nights.
GuideHow to Switch From Night Shift Back to a Day Schedule
After your last night shift, take a short morning sleep, get afternoon daylight and go to bed at a normal hour. Here is how to switch back, days off included.
GuideShould You Sleep Before a Night Shift? (Including Your First One)
Yes: a planned nap of 1.5 to 3 hours in the afternoon or early evening helps you stay alert overnight. Here is how to time it, even for your first night.
Sleep cycles and timing
How Long Does Sleep Inertia Last, and How Do You Shake It Off?
Morning grogginess, or sleep inertia, is worst in the first 15 to 30 minutes and mostly clears within an hour. What makes it worse and what helps it fade.
GuideHow Long Is a Sleep Cycle? Length, Stages and Why It Varies
A sleep cycle lasts about 90 minutes on average, but usually between 80 and 100. Here is what happens in each stage and why the first cycle is shorter.
GuideHow Many Sleep Cycles Do You Need a Night?
Most adults need about five sleep cycles a night, which is roughly 7.5 hours of sleep. See how many fit in 6, 7, 8 and 9 hours, and why total hours matter more.
GuideWhy Do I Wake Up Right Before My Alarm?
Your body can learn when the alarm is due and start a stress-hormone rise about an hour before it. Why it happens, why you may still feel tired, and what to do.
GuideWhy Do I Wake Up Tired Even After 8 Hours of Sleep?
Eight hours in bed is not always eight good hours of sleep. The usual reasons you wake up unrefreshed, from late coffee to a hot room, and when to see a doctor.
Sleep debt
Sleep deprivation
How to Recover From an All-Nighter
Recover from an all-nighter with bright light, a short nap and early caffeine. Skip driving, then sleep a bit early tonight and keep your usual wake time.
GuideIs It Better to Sleep 2 Hours or Stay Up All Night?
For most people, a short sleep beats none: even 90 minutes to 2 hours helps alertness and memory. How to pick 90 minutes vs 3 hours and time the alarm well.
Sleep need
Is 6 Hours of Sleep Enough? (And What About 5 or 7?)
For most adults, 6 hours a night falls short and 5 is too little, while 7 meets the minimum. What two weeks of short nights does, and the rare exceptions.
GuideIs 9 Hours of Sleep Too Much?
Nine hours of sleep can be perfectly normal, especially if you are young, ill or catching up. When long sleep is just your need and when to see a doctor.
Sleep schedule
How to Adjust Your Sleep to Daylight Saving Time (Spring and Fall)
Adjust to daylight saving time by shifting bedtime 15 to 20 minutes a night for a few nights before the change. Why spring is harder and how long it takes.
GuideHow to Fix Your Sleep Schedule (Fast, Without Wrecking a Day)
Fix a sleep schedule by locking in a wake time, getting morning light, dimming evenings and moving bedtime 15 to 30 minutes a day. Skip the all-nighter.