If you feel too hot to sleep when you lie down, your body may not be cooling down

If you toss and turn because you're too hot under the covers and too chilly without them

Key points in 30 seconds

1. Your core body temperature rises and falls over the day, and the drop around bedtime is the signal that says "it's time to sleep."
2. The body releases that heat through the hands and feet. If your face feels hot but your hands and feet are cold, the windows the heat should escape through are closed.
3. In an analysis that pooled 17 studies, even a 10-minute shower or bath in 40–42.5°C water 1–2 hours before bed shortened the time it took to fall asleep and improved sleep quality.
4. Keep the heated mattress pad on only until you fall asleep, use several thin layers of blankets, and cut back on late-night exercise, big meals and alcohol.
5. If you sweat at night enough to soak your pajamas and have a fever or are losing weight, see an internal medicine doctor first.

What we often hear

• "I'm tired all day, but when I lie down I can't fall asleep."
• "With the air conditioner on I'm cold, and with the heated mattress pad on I'm hot."
• "My face feels flushed, but my feet are cold."
• "I keep pulling the covers on and off, and an hour goes by."

You've been tired all day, but once you lie down, sleep won't come.

When you pull up the covers, your body heats up. When you throw them off, you quickly get chilly. With the heated mattress pad on, you're hot. Off, you're cold. Your face feels flushed, but your feet are cold. You toss and turn, and before you know it, an hour has passed.

There's an explanation we often give in the exam room to people who tell us this. To fall asleep, your body needs to cool down a little, and that may not be happening well.

What does sleep have to do with body temperature?

The temperature deep inside your body isn't the same all day. Scientists who study the body clock confirmed long ago that body temperature rises and falls on a roughly 24-hour cycle, just like sleeping and waking.

It stays a little higher during the day, then gradually drops at night as bedtime approaches. This downward drift is the signal that tells your body "it's time to sleep." It stays low while you sleep, then rises again as morning approaches, getting you ready to wake up.

Where does the body release heat?

Through the hands and feet.

Around bedtime, the blood vessels in the palms and soles widen, and heat from inside the body escapes through the hands and feet. The hands and feet are like windows that let out the body's heat. This is also why a sleepy child's hands and feet feel warm when you hold them.

Just as a house cools down only when the windows are open, your core temperature drops and sleep comes only when heat escapes well through your hands and feet.

On the other hand, if your face and torso feel hot and stuffy but your hands and feet are cold, the windows the heat should escape through are closed. It's no coincidence that many people who tell us in the exam room "with the air conditioner on I'm cold, and with the heated mattress pad on I'm hot," or "my face is hot and my hands and feet are cold," have trouble falling asleep. The body isn't doing a good job of spreading heat evenly and letting it out.

Won't a warm bath just make me hotter?

It sounds backward, but warm water actually helps the body cool down.

There's an analysis that pooled 17 studies on how a warm shower or bath before bed affects sleep.

• 1–2 hours before bed
• in water of about 40–42.5°C (about 104–108.5°F)
• for just about 10 minutes

This shortened the time it took to fall asleep, and improved both how well people felt they slept and their sleep efficiency.

When you warm your body in warm water, blood rushes to the palms and soles and the windows open wide. In the hour or two after you get out, heat escapes through those windows, your core temperature drops more easily than usual, and sleep comes riding on that drop.

That's why timing matters. If you take a hot bath right before bed, you'll lie down while your body is still warm. 1–2 hours before bed is best.

What can I try starting tonight?

First, take a warm shower or bath 1–2 hours before going to bed. Warm rather than hot, and 10 minutes is enough. A half-body bath or a foot bath can also help by the same principle, by warming the hands and feet. If you get dizzy or have a heart or blood pressure condition, avoid water that's too hot and long soaks, and stand up slowly when you get out.

Second, keep the heated mattress pad or electric blanket on only until you fall asleep. In winter, many people leave the pad on high all night. But your body needs to stay at a lower temperature even after you fall asleep to sleep deeply. Try warming the bed ahead of time and turning the temperature down when you lie down, or setting a timer so it shuts off after you fall asleep.

Third, keep blankets and pajamas light. Rather than pulling one thick blanket up to your neck, use several thin layers and take one off if you get hot. A bedroom that feels a little cool is better than one that feels warm.

Fourth, cut back on things that heat up your body late at night. Intense exercise right before bed, and big meals or alcohol late at night, can create body heat and get in the way of your temperature dropping. Try to finish exercising early in the evening.

In these cases, something else needs checking first

• If you're a middle-aged woman who keeps waking up at night with a sudden rush of heat and sweating, it may be menopausal hot flashes. We've written about that separately in My face gets flushed and I sleep badly. Is it just my age?.
• If you sweat at night enough to soak your pajamas and have a fever, or are losing weight for no reason, see an internal medicine doctor before treating it as a sleep problem.
• If you snore heavily and have been told you seem to stop breathing while asleep, a sleep apnea test comes first.

How we work

First, we look at your sleep pattern and how your body handles temperature together. With a 1–2 week sleep diary, we check how long it takes you to fall asleep and how often you wake up. We ask in detail whether your hands and feet are cold, whether heat rises to your face and how you sweat, and use blood tests to check things that affect body temperature and sleep, such as thyroid function. We also check for tension with abdominal and pulse diagnosis.

Second, we help your body's regulation and fix your bedtime habits. We release built-up tension with acupuncture and pharmacopuncture (herbal acupuncture), and use herbal medicine matched to your test results and constitution to help your body circulate and release heat evenly. On top of that, we put together lifestyle prescriptions, such as bath timing, mattress pad temperature and blankets, along with bed retraining. Bed retraining is summarized in If you can't sleep, get out of bed.

Third, we check with the sleep diary. Together we look at the records to see whether the time it takes to fall asleep is getting shorter, and whether you're waking up less often from feeling hot or cold. We don't treat without evidence.

What changes

A night when you fall asleep without pulling the covers on and off. A winter night when you don't have to keep changing the temperature of the heated mattress pad.

That's what we aim for.

How fast sleep comes back differs from person to person, depending on how long the insomnia has lasted, your health and your living conditions.

Today's takeaway

To fall asleep, your body needs to cool down, and it releases heat through the hands and feet. Open those windows with a warm shower or bath 1–2 hours before bed.

There are two things to try tonight.

• Take a 10-minute warm shower or bath 1–2 hours before going to bed.
• For a week, write one line a day: roughly how many minutes it took to fall asleep after lying down, and whether you woke up feeling hot or cold. It's also helpful to compare days you bathed with days you didn't.

That record becomes the first map of your sleep. We're open until 8:30 p.m. on weekdays, and on weekends and public holidays too.

The evidence for insomnia treatment is summarized in the director's column Waking up during the night is insomnia too.

For questions or appointments, message us in English through the messenger at the bottom right of the page, or call +82-53-716-1175.

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References

Haghayegh S, Khoshnevis S, Smolensky MH, Diller KR, Castriotta RJ. Before-bedtime passive body heating by warm shower or bath to improve sleep: a systematic review and meta-analysis. Sleep Med Rev. 2019;46:124-135. doi:10.1016/j.smrv.2019.04.008. PMID: 31102877