Why do i get so hot when i sleep: The science of night sweats and overheating

If you keep Googling “why do i get so hot when i sleep” even though your bedroom feels cool, you are not imagining it. Your brain, hormones, muscles, and bedroom setup all play a role — and most of them are fixable.

The relationship

Body heat is not random. In healthy men, core body temperature follows a daily 24-hour rhythm, called a circadian rhythm, that drops in the evening to help you fall asleep and rises again toward morning to help you wake up.^[1] A circadian rhythm is your internal clock that times sleep, hormones, and temperature across the day.

Research in men shows core temperature normally falls by about 0.5–1.0 °C (roughly 1–2 °F) at night, while blood flow to the skin and hands increases so you can dump extra heat into the environment.^[1],[2] That cooling makes it easier for the brain to switch into deep, restorative sleep and supports the release of melatonin, the hormone that signals “night mode.”

When this cooling process is blocked — by a hot room, heavy bedding, alcohol, stress, or medical issues — your brain still tries to hit its target temperature. It does that by opening blood vessels in the skin and turning on sweat glands to offload heat. If the mismatch is big enough, you wake up hot, damp, annoyed, and wondering “why do i get so hot when i sleep when everything looks normal on the thermostat?”

How it works

Your internal clock and core temperature

A region in the brain called the hypothalamus acts as your master clock and thermostat. The hypothalamus is a small deep-brain structure that coordinates hormones, hunger, and temperature. As light fades in the evening, this clock lowers your core temperature set point and signals the body to produce more melatonin, making you feel sleepy and slightly cooler.^[1]

At the same time, your skin, especially on the hands and feet, warms up as blood vessels open. That contrast — cooler core, warmer skin — lets heat move out of the body more easily. Studies show that when the bedroom is too warm or not well ventilated, men spend less time in deep and REM sleep and have more awakenings, even when they do not notice it.^[2]

Thermal environment means the combination of room temperature, bedding, clothing, and air movement that your body experiences during sleep.

Nervous system arousal and stress

The autonomic nervous system is the automatic control network that runs heart rate, sweating, and blood pressure without you thinking about it. Its “fight-or-flight” side, called the sympathetic nervous system, releases stress chemicals like adrenaline and noradrenaline that speed the heart, tighten muscles, and increase sweating.

Night-time stress — from work pressure, arguments, late-night news, or nightmares — keeps that system revved when it should be in “rest-and-digest” mode. When sympathetic activity stays high, skin blood flow and sweating go up, and your brain shifts into lighter, more fragile sleep. Many men who report, “why do i get hot when i sleep only on weekdays?” are feeling this chronic stress pattern more than a thermostat problem.

Adrenaline is a fast-acting stress hormone that prepares your body for action by raising heart rate and boosting blood flow to muscles.

Metabolism, muscle, and body fat

Basal metabolic rate is the number of calories your body burns at rest just to keep you alive. Men usually have a higher basal metabolic rate than women because they tend to carry more muscle mass, and muscle is “expensive” tissue that produces more heat.

Extra body fat changes the equation again. Fat tissue acts as insulation, slowing heat loss from the core to the skin. Obesity in men is linked to higher resting temperature, impaired heat dissipation, and heavier sweating because the body has to work harder to cool itself.

Late, heavy meals and alcohol before bed further boost metabolism and widen blood vessels, which can make you feel flushed and sweaty as your body struggles to process the extra load overnight. If you lift weights or do intense cardio close to bedtime, your already-high metabolic heat may still be peaking when you lie down.

Hormones like thyroid and testosterone

Thyroid hormone is a chemical signal from the thyroid gland in your neck that sets how fast your metabolism runs. In hyperthyroidism, where the thyroid makes too much hormone, men often feel hot, sweaty, jittery, and lose weight even when they are eating normally.^[3] That amped-up metabolism does not shut off at night, so overheating and night sweats are common.

Testosterone is the main male sex hormone that supports libido, muscle, energy, and red blood cell production. When testosterone is chronically low, called hypogonadism, men tend to gain body fat, lose muscle, and develop conditions such as sleep apnea that indirectly raise night-time body temperature. In some men, rapid drops in testosterone from medical treatments can trigger hot flashes and intense night sweats.

Hypogonadism is a condition where the testes do not make enough testosterone for the body’s needs. Testosterone replacement therapy (TRT) is a medically supervised treatment that restores testosterone into a normal range.

Meta analyses indicate that symptomatic men with total testosterone below 350 ng/dL (≈12 nmol/L) are most likely to benefit from TRT. If total testosterone is borderline, measure free testosterone; values below 100 pg/mL (≈10 ng/dL) support hypogonadism. In practice, use 350 ng/dL for total or 100 pg/mL for free as decision thresholds when symptoms persist.

Conditions linked to it

Sometimes the answer to “why do i get hot when i sleep?” is simple: the room is too warm or your comforter is too heavy. Other times, frequent overheating points toward a medical issue that deserves attention, especially in men over 30.

Important conditions that can drive night-time overheating and sweating in men include:

• Obstructive sleep apnea (OSA). OSA is a sleep disorder where your airway repeatedly collapses or narrows during sleep, causing snoring, choking sounds, and drops in oxygen. Men with untreated OSA are significantly more likely to report night sweats and waking overheated because each breathing pause triggers a surge in sympathetic nervous system activity and body temperature.
• Hyperthyroidism and other endocrine disorders. Overactive thyroid, and much more rarely adrenal tumors that overproduce adrenaline, can cause heat intolerance, racing heart, anxiety, and frequent night sweats in men.^[3]
• Overweight, obesity, and metabolic syndrome. Men with a higher body mass index and central belly fat have more insulation and often lower fitness. That combination raises nighttime metabolic heat and increases the risk of OSA, reflux, and other conditions that disturb sleep and temperature control.
• Chronic stress, anxiety, and trauma. Ongoing worry or post-traumatic stress can keep the nervous system in a semi‑alert state all night, leading to spikes of adrenaline, vivid dreams, and hot, sweaty awakenings.
• Medications and substances. Antidepressants, especially SSRIs and SNRIs, as well as some blood pressure drugs and opioids, are known to increase sweating in a subset of men. Alcohol, nicotine, and recreational stimulants can do the same by widening blood vessels and revving up the nervous system.
• Low testosterone and hormone treatments. Long‑standing low testosterone may contribute to night overheating by increasing fat mass and sleep apnea risk. Men on medications that sharply lower testosterone, such as some prostate cancer treatments, can experience sudden hot flashes that feel like intense waves of heat.
• Infections and inflammatory illnesses. Viral infections, tuberculosis, and some inflammatory diseases can cause fevers and drenching night sweats. In men, this is more concerning when sweats are paired with weight loss, fatigue, or persistent cough.

Limitations: much of the research on night sweats relies on self‑reported symptoms from large observational studies, so it can show strong associations — like the link between OSA and sweating — but cannot always prove which problem came first.

Symptoms and signals

Not every warm night is a problem. But certain patterns and symptoms should put “why do i get so hot when i sleep?” on your list of questions for your doctor.

• Needing to throw off the covers or change your T‑shirt most nights of the week.
• Waking up with sheets or pillows soaked from sweat more than once or twice a week.
• Snoring loudly, gasping, choking, or waking with a racing heart or a sense of panic.
• Morning headaches, dry mouth, or feeling “hungover” despite not drinking.
• Unintentional weight loss, fatigue, or loss of appetite alongside night sweats.
• Persistent low libido, erectile changes, or afternoon crashes in energy.
• Fever, body aches, or a new cough in addition to sleeping hot.
• New medications around the time the hot nights started, especially antidepressants or opioids.
• Mood shifts — more irritability, anxiety, or brain fog from broken sleep.

What to do about it

If you are asking “why do i get hot when i sleep?” the goal is not to guess blindly. It is to run a simple, three‑step process: check the basics, rule out medical drivers, then dial in a targeted fix.

1. Get evaluated, not just annoyed.

   Start with a one‑to two‑week log. Each night, jot down room temperature, bedding, what you ate and drank, workouts, stress level, and how often you woke up hot. Bring this to your primary‑care doctor.

   Your clinician may check weight, blood pressure, and neck circumference; listen to your heart and lungs; and order blood tests such as thyroid function, fasting glucose, complete blood count, and morning testosterone.

   For men with fatigue, snoring, or witnessed pauses in breathing, a home sleep apnea test or overnight lab study is often worth it. If low testosterone is suspected, use the thresholds above — total testosterone below 350 ng/dL or free testosterone below 100 pg/mL with symptoms — to guide whether TRT should be discussed.

2. Dial in your sleep setup and habits.

   Environmental tweaks are the fastest wins for many guys who search “why do i get so hot when i sleep, even at 65 degrees?”

   • Keep the bedroom between about 60–67 °F if you can, with a fan or open window to improve air flow.^[2]
   • Switch to breathable bedding like cotton or linen sheets and a lighter comforter; avoid heavy foam toppers that trap heat.
   • Sleep in lightweight, moisture‑wicking shorts or boxers instead of thick pajamas.
   • A warm shower 60–90 minutes before bed can help; as you step out and cool, your core temperature drops and you feel sleepier.
   • Avoid big, spicy, or high‑fat meals and alcohol within 3 hours of bedtime to reduce metabolic heat and flushing.
   • Shift intense workouts to earlier in the day when possible, and use the evening for lighter movement and wind‑down rituals.
   • Build a 20–30 minute pre‑sleep routine that calms the nervous system: dim lights, breathing exercises, reading, or guided relaxation.
3. Treat root causes and track progress.

   Once you have data and basic sleep hygiene in place, work with your doctor to tackle drivers:

   • Sleep apnea: Continuous positive airway pressure (CPAP), oral appliances, weight loss, or positional therapy can reduce apneas and related night sweats.
   • Thyroid issues: If labs show hyperthyroidism, guideline‑based treatment can normalize hormone levels and improve heat intolerance.^[3]
   • Medication side effects: Never stop meds abruptly, but do ask whether dose changes or alternatives could reduce sweating.
   • Low testosterone or androgen therapy: Follow evidence‑based TRT guidelines, and address weight, fitness, and sleep apnea in parallel, not just the lab number.
   • Stress and anxiety: Cognitive behavioral therapy for insomnia and anxiety (CBT‑I/CBT) is strongly supported by evidence and can quiet the “night‑time overdrive” that fuels hot, restless sleep.

   Re‑check your sleep, symptoms, and logs after 4–6 weeks. If you are still waking hot and exhausted, push for a deeper workup with a sleep specialist or endocrinologist.

Myth vs Fact

• Myth: “If I sweat at night, it must be something serious.”
  
  Fact: Most night overheating in men comes from a warm bedroom, heavy bedding, alcohol, or stress. Medical causes exist, but they are not the default.
• Myth: “Colder is always better — I should crank the AC as low as possible.”
  
  Fact: Extremely cold rooms can also disrupt sleep and make it harder for your body’s natural temperature rhythm to work. Aim for comfortably cool, not freezing.^[2]
• Myth: “Alcohol helps me sleep, so it cannot be causing hot nights.”
  
  Fact: Alcohol may knock you out, but it fragments sleep, widens blood vessels, and can lead to sweaty awakenings a few hours later.
• Myth: “Only overweight guys overheat at night.”
  
  Fact: Obesity raises risk, but lean men with hyperthyroidism, high stress, or certain medications can be just as hot and sweaty.^,[3]
• Myth: “If my tests are normal, there is nothing I can do.”
  
  Fact: Even with normal labs, changes in bedroom setup, timing of food and exercise, and stress management often make a big difference.

Bottom line

If you are a man who keeps asking “why do i get so hot when i sleep” or “why do i get hot when i sleep even in a cool room,” your body is sending useful data, not random noise. Night-time overheating usually reflects a mix of your internal clock, stress level, hormones, body composition, and sleep environment. Most of those levers can be adjusted, and serious medical causes can be ruled out with straightforward evaluation. Pay attention, get checked when red flags show up, and then systematically cool the room, calm the brain, and treat any underlying conditions — so your nights feel calm instead of cooked.

References

1. Kräuchi K, Wirz-Justice A. Circadian rhythm of heat production, heart rate, and skin and core temperature under unmasking conditions in men. The American journal of physiology. 1994;267:R819-29. PMID: 8092328
2. Okamoto-Mizuno K, Mizuno K. Effects of thermal environment on sleep and circadian rhythm. Journal of physiological anthropology. 2012;31:14. PMID: 22738673
3. Bahn RS, Burch HB, Cooper DS, et al. Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists. 2011;17:456-520. PMID: 21700562