Feeling a chill as you drift off is usually a sign your body is doing what it’s supposed to do. Falling asleep is tied to a planned drop in your internal temperature, run by your body clock.1PubMed. Body temperature and sleep A few everyday things, from damp bedding to a short night, can turn that normal cooling into a noticeable shiver.
How Your Body Cools Itself Down for Sleep
Core body temperature is the heat deep inside your chest and organs, rather than the warmth on your skin. It falls when mammals sleep.2PubMed. Body temperature and sleep The same brain clock that makes you sleepy at night also sets this daily temperature rhythm, and the two normally move together.3PubMed. Body temperature and sleep The drop starts before you are asleep, as part of getting ready for sleep.
Heat leaves mainly through the hands and feet. Before lights out, blood vessels in the skin there widen and release heat.4PubMed. The thermophysiological cascade leading to sleep initiation in relation to phase of entrainment Losing heat this way makes you sleepy and helps you fall asleep quickly.5PubMed. Functional link between distal vasodilation and sleep-onset latency? So warm hands and feet at bedtime are a sign your body is shedding heat from its core, not holding onto it. If your hands and feet are always icy at bedtime, that is a different pattern, since the heat release is not happening as readily.
That odd mix is why releasing heat can feel like a chill. As warm blood moves out to your skin, your core is cooling while your skin briefly feels warm. Your brain notices the falling core temperature and may react with a brief shiver. It usually comes in the first minutes after lying down, when you stop moving and heat release is picking up. A single short shiver that fades fits this normal process and, on its own, doesn’t point to an illness. A lower core temperature is part of how your body saves energy overnight, which is why a slightly cool room feels easier to fall asleep in than a hot one.
For the same reason, a light cover works best at this stage. Your skin needs to lose heat, so heavy bedding piled on too early can work against the drop. A light layer you can add to once the chill passes lets cooling happen and keeps you comfortable. If you do get chilled, an extra layer on the feet or shoulders is often enough, with no need to bundle up completely.
Why Your Body Stops Defending Its Temperature in Dream Sleep
In deep sleep, your body’s systems, including temperature control, shift toward saving energy.6Comprehensive Physiology. Thermoregulation and Sleep: Functional Interaction and Central Nervous Control Dream sleep, also called REM sleep, is different: your heart rate, breathing and temperature control become unsteady.7Comprehensive Physiology. Thermoregulation and Sleep: Functional Interaction and Central Nervous Control Your body temperature then drifts with your surroundings instead of being held steady.8PubMed Central. REM Sleep and Endothermy: Potential Sites and Mechanism of a Reciprocal Interference In a cool room, you can wake from a dream feeling chilled even though you were warm when you fell asleep.
Dream sleep comes in cycles roughly every 90 minutes, and the periods get longer toward morning. Waking with cold shoulders or feet in the early hours often follows one of them. Thrown-off covers matter more during these stretches, because your body won’t shiver to correct the loss. Shivering is one of its main ways of fixing a falling temperature, and it is largely switched off in REM sleep.
Keep a spare blanket within arm’s reach so you can add warmth in the half-awake moment instead of lying cold. Choose bedding that stays on you, such as a tucked sheet or a heavier cover at the foot. And set the room a little warmer for the early-morning hours, since the room is often coolest then.
Short Sleep Makes Chills Stronger
After one sleepless night, core temperature runs lower.9PubMed. Sleep deprivation alters body temperature dynamics to mild cooling and heating not sweating threshold in women A sleep-deprived body also loses heat quickly when it meets even mild cooling,10PubMed. Sleep deprivation alters body temperature dynamics to mild cooling and heating not sweating threshold in women so you may struggle to warm up in a room that would normally feel comfortable.11PubMed. Sleep deprivation alters body temperature dynamics to mild cooling and heating not sweating threshold in women Missing sleep also throws off the balance between hands and feet, with less heat leaving the hands and more leaving the feet.12PubMed Central. Cold Hands, Warm Feet: Sleep Deprivation Disrupts Thermoregulation and Its Association with Vigilance
A bad night makes the next bedtime feel colder, and feeling cold makes it harder to fall asleep, which shortens sleep again. Warm socks or extra layers break that loop more easily than waiting it out.
Broken or irregular sleep, as with shift workers and new parents, is a common reason people notice chills only at certain times. The effect is strongest when your body is already cooling, at bedtime and in the early morning. It usually eases once you catch up on sleep.
On a bad-sleep day, keep the evening routine the same, since a regular bedtime helps your body clock stay on track. Skip a long nap late in the day, because it can push your next bedtime later and keep the poor-sleep pattern going.
Damp Bedding and a Too-Cool Room
Bedding that doesn’t let moisture escape can hold sweat close to your skin, then cool you suddenly as that sweat evaporates.13Sierra Dreams. Why Do I Get Chills at Night? Yet a slightly cool bedroom actually helps your body shed heat and fall asleep.14PubMed Central. Thermoregulation in Sleep Disorders—Comprehensive Review So the aim is a cool room with breathable, dry bedding, not a hot room. A mattress that draws heat away from your body can also deepen sleep and reduce waking.15PubMed Central. Thermoregulation in Sleep Disorders—Comprehensive Review
The chill is strongest if you throw off the covers or turn over while damp, because air reaches the wet skin. Sleepwear can be part of the problem too, since a damp shirt stays against your skin.
Signs that bedding is the cause: you feel clammy, then cold, especially under heavy synthetic duvets, and the chills come after you first warm up under the covers rather than straight away. Several lighter layers let you adjust through the night, while a single thick cover tends to cause sweating and then chilling. Switching to cotton or wool layers you can add or remove often helps.
Feel your sheets and pajamas when you wake chilled. If they are damp, moisture is probably the cause. If the bed is dry and you still get chills, bedding is less likely to be the culprit and the other causes here deserve a look.
Hot Flushes, Low Blood Sugar, Fever and Medicines
After a hot flush, a woman in perimenopause or menopause can feel chilled as the sweat dries, and some women call these “cold sweats.”16CeMCOR. Perimenopause and Thyroid Problems—common and confusing Damp sheets and a sudden warm feeling in the face, neck and chest before the chill are typical of this pattern. Thyroid-related coldness is different, because it isn’t preceded by a wave of heat and sweating.17CeMCOR. Perimenopause and Thyroid Problems—common and confusing
When blood sugar drops too low at night, stress hormones such as adrenaline surge to bring it back up.18NeuroLaunch.com. Shaking When Waking Up from Sleep: Causes, Treatments, and When to Seek Help That can cause shaking, sweating and a racing heart.19NeuroLaunch.com. Shaking When Waking Up from Sleep: Causes, Treatments, and When to Seek Help In one test of low blood sugar, people mostly reported feeling sweaty, not cold.20PubMed. Metabolic and cutaneous events associated with hypoglycemia detected by sleep sentry So shaky, sweaty waking is a stronger hint of low sugar than plain chills, especially if you use insulin or diabetes medicines. If it happens, check your blood sugar if you have a meter and follow the plan your care team gave you.
The immune signals that raise your temperature during an infection also push you toward deep sleep.21NeuroLaunch.com. Sleeping with a Fever: Effective Strategies for Rest and Recovery So chills while drifting off when you are ill can mean a fever is climbing. A rising fever feels cold because the body has set a higher temperature target, and your current temperature feels cold by comparison. If you feel unwell and chilly at bedtime, take your temperature with a thermometer instead of guessing. A normal reading with no other symptoms points back toward the everyday causes.
Antidepressants such as sertraline (Zoloft), paroxetine (Paxil), venlafaxine (Effexor) and duloxetine (Cymbalta) can change how your body controls its temperature and sweating, so night sweats followed by chills can be a side effect worth raising with your prescriber.22The Checkup. 5 medications that lower your body temperature
How to Stop Feeling Cold as You Fall Asleep
Wearing bed socks through the night helped people in a cool room fall asleep faster and stay more relaxed.23PubMed Central. Effects of feet warming using bed socks on sleep quality and thermoregulatory responses in a cool environment A warm foot bath before bed can shorten the time it takes to fall asleep for people with cold hands and feet.24PubMed Central. Thermoregulation in Sleep Disorders—Comprehensive Review Warm water widens the blood vessels in the feet so they can release heat afterward.
A simple routine: soak your feet in warm water for 10 to 15 minutes, then dry them well. Put on loose socks that don’t squeeze. Set the room on the cool side and use layered, breathable covers. Avoid getting into bed straight after a cold shower.
Socks matter in the details. Loose socks let blood flow freely, and tight elastic can work against the warming effect. Soft wool or cotton blends breathe, so feet don’t get sweaty. If your feet get too warm and you wake up sweaty, take them off or switch to a thinner pair.
Going to bed hungry after a fast leads to a lower body temperature overnight than eating an evening meal.25PubMed. Energy content of the evening meal alters nocturnal body temperature but not sleep A bigger meal didn’t improve sleep itself, though.26PubMed. Energy content of the evening meal alters nocturnal body temperature but not sleep So a normal dinner rather than skipping food may ease chills, without needing a heavy meal.
When Chills at Night Need a Doctor
Chills along with a fever that lasts more than a few days need a medical check. So do drenching night sweats, weight loss you can’t explain, or feeling cold all day long. If you take insulin or diabetes medicines, discuss shaky, sweaty waking with your doctor, because it can mean low blood sugar. And don’t stop an antidepressant on your own; ask your prescriber about temperature side effects.
Before an appointment, note what time the chills happen and how long they last, and whether heat or sweat came first. List your medicines and any recent changes, and note how you slept the night before.
Chills with a high fever, confusion, or trouble breathing call for urgent care rather than waiting for an appointment. A pattern that has gone on for weeks, even without those signs, is worth a routine visit. If you are unsure whether something counts as a warning sign, it is reasonable to call the doctor’s office and ask.