Feeling hot and then cold in the same hour is your body’s thermostat doing its job — sometimes too aggressively. A fever, hormonal shifts, anxiety, and certain medications can all reset your internal temperature set point or confuse the signals your body uses to regulate heat. The pattern of your hot-cold swings — when they happen, how long they last, and what comes with them — is what points to the cause.
Why Am I Getting Hot And Cold?
Your body keeps its core temperature within a narrow range, roughly 97°F to 99°F (36.1°C to 37.2°C) for most adults. A small structure in your brain called the hypothalamus acts as the thermostat. When it decides you need to be warmer, it triggers shivering and blood vessel narrowing to trap heat. When it decides you need to cool down, it triggers sweating and blood vessel widening to release heat.
Hot and cold sensations happen when that system gets pushed in one direction and then the other. Two different things are usually going on:
- Your actual core temperature is changing — like during a fever, when your set point rises and then falls
- Your set point is stable but your body is overreacting — like hot flashes, anxiety, or a panic response
You can usually tell which one you are dealing with by whether you have a measurable fever. A thermometer reading above 100.4°F (38°C) points toward the first category. Normal temperature with intense hot-cold sensations points toward the second.
What Causes Hot And Cold Flashes?
Fever is the most common cause of alternating hot and cold feelings, and it is worth understanding how it actually works. When your immune system detects an infection, it releases chemicals called pyrogens that tell the hypothalamus to raise your set point. You feel cold and start shivering because your body is now trying to reach a higher target temperature. Once the fever breaks, the set point drops back down and you feel hot and sweaty as your body dumps the extra heat.
Other common causes fall into a few groups:
- Hormonal changes — especially the drop in estrogen around perimenopause and menopause, which is a well-documented trigger for hot flashes and chills
- Anxiety and panic — the fight-or-flight response redirects blood flow and can produce a sudden wave of heat followed by chills
- Medications — some antidepressants, opioids, and blood pressure drugs can affect temperature regulation
- Thyroid problems — an overactive thyroid tends to cause heat intolerance, while an underactive thyroid tends to cause cold intolerance
- Blood sugar swings — low blood sugar can cause sweating and shakiness that feel like temperature changes
Some causes are more serious. Infections, certain cancers, and autoimmune conditions can all produce fever and night sweats. This is why persistent unexplained hot-cold episodes deserve a medical evaluation rather than a wait-and-see approach.
Why Do I Get Hot And Cold At Night?
Night sweats and chills are common and usually not dangerous, but the pattern matters. Body temperature naturally dips in the early morning hours as part of your circadian rhythm, and that normal dip can feel exaggerated when something else is already affecting your thermostat.
Common reasons for nighttime hot-cold swings include:
- Hormonal changes, particularly in perimenopause and menopause
- Infections, including mild ones
- Anxiety or vivid dreams that trigger a stress response
- Medications such as antidepressants
- Alcohol, which widens blood vessels and disrupts sleep temperature regulation
- Room temperature and bedding that trap too much heat
Night sweats that soak through clothing or bedding, happen most nights, or come with unexplained weight loss, fever, or swollen lymph nodes are worth a prompt medical visit. Those combinations have a broader list of possible causes and need proper evaluation.
When Is Feeling Hot And Cold A Sign Of Something Serious?
Most hot-cold episodes are not emergencies. But some patterns need medical attention quickly. Seek care if you have:
- A fever above 103°F (39.4°C) in adults, or any fever with a stiff neck, confusion, or a severe headache
- Fever with a rash, difficulty breathing, or chest pain
- Fever in an infant under 3 months old — this is always a medical emergency
- Night sweats that soak bedding, especially with weight loss or swollen lymph nodes
- Hot-cold episodes with heart palpitations, tremor, or unexplained weight loss, which can point to thyroid problems
- Fever that lasts more than a few days without a clear cause
Fevers are the body’s normal response to infection and are not dangerous by themselves in most healthy adults. The concern is not the temperature alone but what is driving it and what other symptoms come with it.
How Are Hot And Cold Episodes Evaluated?
A doctor will usually start with a detailed history — when the episodes happen, how long they last, what triggers them, and what other symptoms show up. That history often narrows the cause more than any test.
Depending on what they find, common next steps include:
- Measuring your temperature during an episode
- Blood tests to check thyroid function, blood sugar, and markers of infection or inflammation
- Hormone testing if perimenopause or menopause is suspected
- Reviewing your medications for ones that affect temperature regulation
There is no single test for “hot and cold flashes.” The evaluation is about ruling in or out specific causes based on your pattern and history.
What Helps With Hot And Cold Flashes?
What helps depends on the cause. For fever, the goal is comfort and monitoring, not forcing the temperature down unless it is high or you are uncomfortable. Drinking fluids, resting, and using light layers rather than heavy blankets can help. Over-the-counter fever reducers like acetaminophen or ibuprofen can lower a fever, but they treat the symptom, not the underlying cause.
For hormonal hot flashes, some people find relief from lifestyle changes like avoiding triggers (spicy food, alcohol, caffeine), keeping the room cool, and dressing in layers. Prescription options exist for moderate to severe menopause symptoms, and a doctor can discuss whether they are appropriate.
For anxiety-related temperature swings, addressing the anxiety itself — through therapy, breathing techniques, or medication — is usually what reduces the episodes.
No single remedy works for everyone, and what helps depends heavily on what is causing the problem. If you are not sure of the cause, that is the first thing to sort out.
Frequently Asked Questions
Why do I feel hot and cold at the same time?
Feeling hot and cold at once usually means your body is trying to raise its temperature — you feel cold and shiver while your skin feels hot to the touch. This is common at the start of a fever or during a hot flash.
Can anxiety cause hot and cold flashes?
Yes. Anxiety and panic trigger the fight-or-flight response, which shifts blood flow and can cause a sudden wave of heat followed by chills. These episodes typically pass within minutes once the stress response settles.
When should I worry about hot and cold flashes?
See a doctor if episodes come with a fever above 103°F, night sweats that soak your bedding, unexplained weight loss, or swollen lymph nodes. Persistent episodes without a clear cause also deserve evaluation.
Are hot and cold flashes a sign of menopause?
They can be. Hot flashes and chills are common during perimenopause and menopause because of falling estrogen levels. But the same symptoms have many other causes, so they are not proof of menopause on their own.
