You’re sitting on the couch, minding your own business, when suddenly your chest feels like it’s glowing. Not the "warm and fuzzy" kind of glow, but a prickly, radiating heat that makes you want to rip your shirt off. You reach for the AC remote. Two minutes later? You’re shivering. You’re hunting for that wool blanket you shoved into the back of the closet last spring. It’s annoying. It’s also incredibly common. Feeling hot then cold isn't just a "quirk" of your personality; it’s usually a signal that your hypothalamus—the dime-sized portion of your brain acting as a smart thermostat—is getting mixed signals.
Sometimes it’s just the room. Most of the time, it’s biology.
The Hypothalamus and the "Set Point" Problem
Think of your body like a high-end HVAC system. Under normal conditions, your internal temperature stays right around 98.6°F (37°C), though "normal" is actually a sliding scale. When you start feeling hot then cold, what’s actually happening is a shift in your "set point."
If your brain suddenly decides your set point should be 102°F because it senses an invader, your current 98.6°F feels freezing. You shiver to generate heat. Once you hit that new high, or if the "order" is rescinded, you suddenly feel like you’re overheating. You sweat to cool down. It’s a literal see-saw.
This isn't always about a flu, though. Dr. Sharon Malone, a board-certified OB/GYN and chief medical officer at Alloy Women’s Health, often points out that for many, these "vasomotor symptoms" are the hallmark of perimenopause. It’s not just "getting old." It’s a complex neurological response to dropping estrogen levels that tricks the brain into thinking the body is overheating when it isn't.
The Adrenaline Spike You Didn't Ask For
Anxiety is a physical beast.
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When you’re stressed, your "fight or flight" reflex kicks in. Adrenaline floods the system. This pushes blood toward your core and vital organs, away from your skin. You might feel a sudden rush of heat—the "hot flash" of anger or panic—followed immediately by a chill as that blood retreats and your sweat evaporates. If you’ve ever had a panic attack and ended up huddled under a duvet afterwards, that’s why. Your body spent all its energy preparing for a tiger that wasn't there, and now you’re physically exhausted and cold.
Why Hormones Create a Temperature Rollercoaster
If you’re a woman in your late 30s or 40s, feeling hot then cold is almost certainly tied to the endocrine system. It’s the classic hot flash-chills cycle.
But men aren't exempt. Low testosterone (hypogonadism) can cause remarkably similar symptoms. When testosterone levels crater, the hypothalamus becomes hypersensitive. It overreacts to tiny changes in ambient temperature. You’re fine one minute, then you’re drenching your work shirt the next. It’s disruptive. It’s frustrating. And honestly, it’s hard to explain to people who aren't experiencing it.
- The Estrogen Drop: Estrogen helps regulate the hypothalamus. When it fluctuates during the menstrual cycle or perimenopause, the "cooling" mechanism triggers too easily.
- Thyroid Issues: Your thyroid is the battery of your metabolism. An overactive thyroid (hyperthyroidism) makes you feel like you’re burning up. If it’s swinging back and forth, or if you have Hashimoto's, you might bounce between feeling like an oven and an icebox.
- Post-Viral Fatigue: We’ve seen this a lot recently. Long-term recovery from viruses can leave the autonomic nervous system—the part that handles things you don't think about, like breathing and temp control—totally out of whack.
The Role of Blood Sugar and Diet
Ever had a "sugar crash"? It’s real.
When your blood sugar spikes and then plummets (reactive hypoglycemia), your body releases epinephrine to try and stabilize things. This causes shakiness, sweating, and—you guessed it—chills. If you find yourself feeling hot then cold about two hours after a heavy pasta lunch or a sugary Starbucks drink, look at your glucose levels. It’s a metabolic hiccup.
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Alcohol is another huge culprit. People think a "nightcap" warms them up. It doesn't. Alcohol is a vasodilator. It brings blood to the surface of your skin, which makes you feel warm temporarily but actually causes you to lose core body heat rapidly. Once that initial "flush" wears off, you’re left colder than you were before you had the drink. Plus, the way the liver processes alcohol can trigger night sweats, leading to that miserable "kick the covers off, pull the covers on" dance all night long.
Infections You Might Be Ignoring
We all know the "chills and fever" routine of a standard cold. But chronic, low-grade infections can cause persistent temperature swings without ever making you feel "sick" enough to stay in bed.
Urinary tract infections (UTIs), especially in older adults, often present as sudden temperature shifts or confusion rather than the typical burning sensation. Similarly, certain lingering dental infections or even tuberculosis (which is making a quiet comeback in some regions) can cause "night sweats" and daytime chills. If the cycling between hot and cold persists for more than a couple of weeks without a clear cause, it’s time to stop Googling and start booking a blood test.
Anemia and Iron Deficiency
Let's talk about iron. Iron is what allows your blood to carry oxygen. If you’re anemic, your body struggles with thermoregulation. You’ll often feel cold to the bone, particularly in your hands and feet. But because your heart has to work harder to pump that oxygen-poor blood, you might also experience bouts of "overheating" or palpitations. It’s a confusing mix of signals. According to the Mayo Clinic, iron deficiency is one of the most common nutritional deficiencies, yet people often overlook it as a cause for feeling "temperature-unstable."
Practical Ways to Stabilize Your Body Temp
You can't always fix the underlying cause instantly, but you can manage the sensation.
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Layering is a science, not just a fashion choice. Stick to natural fibers like merino wool or silk. These materials are "moisture-wicking," meaning they pull sweat away from your skin so it doesn't sit there and turn into a cold, clammy layer that gives you the shivers. Synthetics like polyester often trap heat, making the "hot" phase feel suffocating.
Check your meds. A lot of common prescriptions mess with your internal thermostat. Antidepressants (specifically SSRIs like Lexapro or Zoloft) are notorious for causing increased sweating and heat sensitivity. Even OTC meds like ibuprofen can cause a "rebound" effect where your temp drops as the drug wears off, making you feel chilled.
The "Cold Water" Trick.
If you feel a hot flash coming on, try running cold water over your wrists for 30 seconds. There are major arteries close to the skin there. Cooling that blood can help signal the brain that the "emergency" is over, potentially dampening the intensity of the following cold snap.
When to Actually Worry
Most of the time, feeling hot then cold is a lifestyle or hormonal issue. However, there are "red flags." If your temperature swings are accompanied by unexplained weight loss, drenching sweats that require you to change your pajamas, or a persistent lump anywhere on your body, see a doctor. These can be early signs of lymphoma or other systemic issues that need a professional eye.
Actionable Steps for Better Temperature Control
Start tracking the timing. Does it happen after meals? During your period? When you’re stressed at work?
- Audit your caffeine intake. Caffeine constricts blood vessels and can trigger the "hot then cold" cycle by stressing the adrenal glands. Cut back for three days and see if the swings stabilize.
- Hydrate aggressively. Dehydration makes it much harder for your body to regulate its temperature. If you don't have enough fluid, you can't sweat efficiently to cool down, and your blood volume drops, making you feel cold.
- Optimize your sleep environment. Use "cool-to-the-touch" bedding if you deal with night sweats. Keeping the room at a steady 65-68°F is generally considered the "sweet spot" for most people's thermoregulation.
- Request a full thyroid panel. Don't just get a TSH test; ask for Free T3, Free T4, and antibodies. Often, a "normal" TSH masks a thyroid that’s struggling to keep up with daily demands.
Addressing the cycle of feeling hot then cold requires looking at your body as a whole system rather than just a broken thermostat. Whether it’s balancing hormones, stabilizing blood sugar, or managing the physical manifestations of anxiety, getting back to a steady "middle ground" is possible once you identify the trigger.