Waking up tired can leave you wondering what happened overnight, and whether REM sleep has anything to do with it. It's an understandable question when you've spent hours in bed but still feel worn out. That feeling alone doesn't tell you how much time you spent in any particular sleep stage. Start with how the night went overall before pinning a rough morning on REM.
REM sleep in brief
REM sleep is the stage when your eyes move rapidly, most muscles are switched off and your brain stays busy; most dreaming happens here. The best evidence links it to memory and reorganising what you've learned while awake. My advice is to give it more time: sleep longer and keep regular hours rather than buy something to boost it.
REM is the rapid eye movement stage of sleep
REM stands for rapid eye movement, a stage of sleep that returns several times a night and lasts longer towards morning. During REM, your brain is highly active, and this is the stage from which most dreaming is reported. Most of your muscles are temporarily switched off so you don't act out your dreams, even though your eyes can still move beneath closed lids.
REM returns several times a night, and the periods get longer towards morning.
Those eye movements can follow the action in a dream. In Leclair-Visonneau and colleagues' 2010 study, eye movements matched the direction of dream actions in 82% of goal-directed sequences, meaning dream actions the participants acted out.3 The participants had REM sleep behaviour disorder, in which the usual muscle paralysis fails. This let researchers compare their eye movements with the actions they performed while dreaming. The finding applies to this particular group; it doesn't establish that every eye movement follows a dream. I wouldn't try to decode someone's dreams by watching their eyes.
What REM sleep does
The best-supported job of REM sleep is memory, with research looking at how it relates to performance after sleep. In Lau's 2015 nap study, working-memory accuracy rose with both the amount of REM sleep and total sleep during the nap.2 Working memory is what you use to hold information in mind while you're doing something with it, such as following instructions.
Bieth (2026) links REM sleep to the brain reorganising associations related to a problem you'd been working on.1 Together, these findings support a role in memory and problem solving; they don't establish that adding REM will improve your memory or guarantee a solution. I take that as a sensible version of "sleep on it": give yourself a chance to return to a problem after sleep, without expecting the answer to arrive overnight.
How much REM sleep do you need?
There's no set nightly amount of REM sleep to aim for. The share of sleep spent in REM falls as adults get older, according to Ohayon and colleagues' 2004 meta-analysis.4 I wouldn't treat a fixed REM target as a nightly pass or fail.
Give yourself longer to sleep if you want more REM. REM periods lengthen later in the night, so an early alarm cuts off the part of your sleep richest in REM. Sleeping longer is the surest way to give yourself more of that time.
Sleep long enough and keep regular hours to get more REM
The NHS says adults need 7 to 9 hours of sleep on average, and you probably aren't getting enough if you're constantly tired during the day.6 Sleep that long and the REM-rich last hours take care of themselves.
Follow the NHS advice: wake up and get out of bed at the same time every day, the one habit that keeps the rest of the night in place. Exercise regularly during the day, but not within 4 hours of bed, and don't eat a big meal late at night. For me, a regular wake time does more than any gadget.
Sleep trackers estimate REM sleep
Wearables and sleep apps estimate sleep stages from movement and heart rate rather than reading brain activity the way a sleep lab does. Treat the REM figure as a rough trend over weeks, not a nightly score. I wouldn't let that number decide whether I'd slept well.
Look at total sleep and regular timings first: these give you a more useful starting point than an estimate of one sleep stage. If you're worried about how you're sleeping, and not just about a tracker number, talk to your GP.
Do foods or supplements boost REM sleep?
No food or supplement has good evidence of increasing REM sleep, so skip the tryptophan, magnesium and B6 shopping list. In the UK, melatonin isn't sold over the counter, and the NHS states: "Melatonin is available on prescription only."
Alcohol is the diet change I'd focus on. Ebrahim and colleagues' 2013 review found that alcohol delays the first REM period at all doses studied; at moderate and high doses, most studies found less REM across the night.5 Alcohol also disrupts the second half of the night. If you want more REM, leave a gap between your last drink and bed.
Questions people ask about REM sleep
Is REM the deepest stage of sleep?
No, deep sleep usually refers to slow-wave sleep; your brain is busiest during REM. These are different stages, so more brain activity doesn't mean you're missing out on proper sleep. I wouldn't read "deep" as "better" and aim to spend every hour there. You don't need to choose between deep sleep and REM: both are part of a night's sleep.
Why do I remember more dreams in the morning?
You remember morning dreams more easily because your longest REM periods occur later in the night. Dreams are reported most often when people wake from REM, so waking at that point gives you more chance of recalling one. If you want to remember a dream, I'd jot it down as soon as you wake.
Does alcohol affect REM sleep?
Yes, alcohol delays REM and, at moderate or high doses, reduces total REM in most studies, as described above. Leave some time between your final drink and going to bed, because the sleepy feeling after alcohol doesn't mean better sleep: drinking also disturbs sleep in the second half of the night.
Should I see a doctor about my REM sleep?
See your GP when poor sleep affects your daytime life, rather than for a tracker reading alone. You don't have to identify a problem with REM before asking for help. Before the appointment, note how long you take to fall asleep and how often you wake. I'd also write down how you feel during the day, so you can explain what the poor sleep means for you.
