Last Updated on May 28, 2025 by Analgesia team
Have you ever been perfectly fine one moment—then suddenly, you’re shivering under a blanket or wiping away unexpected sweat?
This isn’t just in your head. Sudden changes in body temperature are more common than most people realise, and they can leave you confused, uncomfortable, or even worried. What’s going on inside your body that flips your internal thermostat like a light switch?
Let’s break it down.
Body temperature is one of the most tightly regulated systems in the human body. While slight fluctuations throughout the day are normal, sharp or frequent changes—like chills without a fever, feeling overheated at rest, or alternating hot and cold spells—could signal something deeper.
In this post, we’ll explore why your body temperature might suddenly change—from common causes like hormonal shifts and infections to more complex triggers such as electrolyte imbalances, magnesium deficiency, and chronic illness. You’ll also learn when to worry, what to do about it, and how to bring your body’s thermostat back into balance.
So if your internal temperature keeps you guessing, this guide will help you understand what it means—and what you can do about it.
What’s Considered a ‘Normal’ Body Temperature?
We often hear that 98.6°F (or 37°C) is the “normal” body temperature—but the truth is, normal isn’t a fixed number.
Your body temperature naturally shifts throughout the day depending on your activity level, sleep cycle, hormones, and even the weather. In fact, a healthy range typically falls between 97°F to 99°F (36.1°C to 37.2°C) for most adults.
But here’s where it gets interesting.
- Your lowest temperature usually occurs in the early morning.
- Your highest? Late afternoon or early evening.
- Women may experience subtle changes during different phases of their menstrual cycle, especially around ovulation.
- Older adults often run slightly cooler than younger people.
So when should a temperature change raise concern?
It’s all about the pattern and intensity. If you’re experiencing sharp, recurring changes—like sweating one moment and shivering the next—it could be a clue that something is affecting your body’s temperature regulation system, also known as thermoregulation.
Next, let’s explore what causes these sudden shifts—starting with one of the most overlooked triggers: your hormones.
Common Causes of Sudden Changes in Body Temperature
Your body’s internal thermostat is influenced by several harmonious systems—especially your hormones, immune response, electrolytes, and nervous system. When even one of these systems is thrown off balance, you might feel unexpectedly cold or hot, even if the room temperature hasn’t changed.
Let’s break down the most common reasons:
a. Hormonal Fluctuations
Hormones act like chemical messengers—and some of them have a powerful effect on body temperature regulation.
In women, estrogen and progesterone levels shift during the menstrual cycle, pregnancy, and menopause. These changes can cause hot flashes, night sweats, or even episodes of feeling unusually cold.
For example:
During menopause, declining estrogen levels interfere with the hypothalamus (your internal thermostat), causing sudden hot flashes—even in cool environments.
Thyroid hormones are another key player. The thyroid gland regulates your metabolism—and your body temperature is part of that equation.
- Hyperthyroidism (overactive thyroid) speeds up metabolism, causing heat intolerance, sweating, and flushed skin.
- Hypothyroidism (underactive thyroid) slows metabolism, leading to cold sensitivity, chills, and dry skin.
Quick tip: If you’re often cold while others are warm—or vice versa—it might be time to check your thyroid levels.
b. Infections and Immune Response
When your body detects an infection, it doesn’t wait around.
It kicks your immune system into high gear, and a big part of that defence mechanism involves changing your body temperature—often in the form of fever or chills.
But here’s the twist…
Not all infections cause an obvious fever. Some cause low-grade fevers, while others create an up-and-down pattern—feeling hot one moment and chilled the next.
Common culprits include:
- Flu or cold viruses
- Urinary tract infections (UTIs)
- COVID-19 and other respiratory infections
- Hidden or chronic infections, like Lyme disease or tuberculosis
Even post-viral fatigue can cause temperature fluctuations, especially in long COVID cases, where people report random waves of overheating or cold sensations months after infection.
Still not sure what’s behind your strange chills or sweats?
Let’s explore another often-overlooked factor—your electrolytes.
c. Electrolyte Imbalances (Magnesium, Potassium & More)
Electrolytes are minerals—like magnesium, potassium, sodium, and calcium—that carry an electric charge and help regulate nerve signals, muscle contractions, and yes, your body temperature.
When these minerals fall out of balance, your “internal thermostat” can go haywire:
- Magnesium Deficiency
Low magnesium can impair the body’s ability to generate heat in response to cold, and it may also worsen hot flashes or night sweats.
If you’ve been reading about electrolyte support, you know that magnesium helps potassium stay in your cells—so a lack of magnesium can lead to both thermal and cramp issues. - Potassium Imbalance
Potassium helps your cells maintain fluid balance. Too little, and you might feel chilled; too much, and you could experience warmth or flushing. - Sodium and Calcium Shifts
Hyponatraemia (low sodium) often causes chills and shivering, while hypercalcaemia (high calcium) may produce sweating and heat intolerance.
Why this matters:
Small shifts in these electrolytes—common in dehydration, heavy sweating, or poor diet—can send confusing signals to your hypothalamus, leading to sporadic hot or cold spells.
Quick fix: Rehydrate with electrolyte-rich fluids (coconut water, electrolyte tablets) and include magnesium‑ and potassium‑rich foods (leafy greens, beans, nuts) in your diet.
d. Nervous System Dysregulation (Especially the Autonomic System)
Your autonomic nervous system (ANS) controls automatic functions like breathing, heart rate, digestion—and yes, temperature regulation. When the ANS is disrupted, the body can send mixed signals, making you feel hot without a fever, or cold in a warm room.
This dysregulation is often seen in conditions like:
- Postural Orthostatic Tachycardia Syndrome (POTS)
Many people with POTS experience heat intolerance, cold sweats, or sudden flushing due to poor blood flow and nervous system imbalance. - Fibromyalgia and Chronic Fatigue Syndrome (CFS/ME)
These conditions can interfere with the body’s ability to regulate temperature, leading to cold hands/feet, burning sensations, or rapid swings between chills and warmth. - Anxiety or Panic Disorders
Ever felt flushed or sweaty during a stressful moment? That’s your sympathetic nervous system kicking in, flooding your body with adrenaline and triggering temperature changes.
So how do you know whether it’s your nerves or something else?
Let’s look at one more key factor—medications and lifestyle choices that might be throwing off your internal balance.
e. Medications, Stimulants, and Lifestyle Factors
Sometimes, the culprit behind sudden temperature swings isn’t a medical condition—it’s your daily habits or the pills in your cabinet.
Let’s take a closer look:
- Medications
Certain drugs directly affect how your body manages heat:- Antidepressants (like SSRIs) can interfere with the brain’s temperature regulation.
- Hormone therapy, including HRT and birth control, may trigger hot flashes or night sweats.
- Blood pressure medications (like beta-blockers) can reduce blood flow to the skin, making you feel cold.
- Diuretics may cause electrolyte imbalances that affect thermal control.
- Stimulants
Substances like caffeine, nicotine, and certain weight-loss products can raise body temperature temporarily by increasing metabolism and heart rate. - Alcohol
Alcohol causes blood vessels to dilate—creating a false sense of warmth—but can actually drop your core body temperature. - Poor Sleep, Stress, and Sedentary Lifestyle
Chronic stress and lack of sleep increase cortisol, which can interfere with thermoregulation. Likewise, inactivity may impair circulation and worsen heat or cold sensitivity.
Pro tip:
Check the side effects of any new medication, especially if your symptoms started after a change in prescription or routine.
How to Manage Fluctuating Body Temperature Naturally
Feeling hot one minute and cold the next? Here’s how to regain control—naturally, gently, and effectively.
1. Restore Electrolyte Balance
Electrolytes are essential for regulating temperature. Even mild dehydration or deficiency can throw things off.
Do this:
- Drink electrolyte-rich fluids like coconut water, bone broth, or DIY electrolyte drinks.
- Eat magnesium-rich foods like spinach, pumpkin seeds, almonds.
- Include potassium sources: bananas, sweet potatoes, beans, and avocados.
- Consider Natural Calm magnesium powder or gummies if your diet is lacking.
2. Support Your Nervous System
Since the autonomic nervous system plays a big role in thermoregulation, keeping it in balance is key.
Try this:
- Practice deep breathing or yoga to calm sympathetic overdrive.
- Get regular, light exercise—walking, stretching, swimming.
- Prioritise good sleep hygiene to lower cortisol and stabilise your core temperature.
- Reduce caffeine and alcohol, which can cause spikes and crashes.
3. Address Underlying Conditions
If your temperature swings are tied to other symptoms—like fatigue, anxiety, or hormonal shifts—it may signal a deeper issue.
Important:
Consult your doctor if you suspect:
- Thyroid dysfunction
- Hormonal imbalances
- Chronic infections
- Fibromyalgia or dysautonomia (e.g. POTS)
Still unsure what’s causing it? Don’t guess—get tested.
4. Review Medications and Supplements
Sometimes the cause is sitting right in your pillbox.
Here’s what to do:
- Check with your GP or pharmacist if a medication might be causing heat/cold sensitivity.
- Never stop a prescription suddenly—some drugs need to be tapered off.
- If taking multiple supplements, especially hormonal or stimulating ones, consider simplifying your routine to see if symptoms improve.
5. Use Practical Day-to-Day Tools
Simple fixes can go a long way:
- Dress in layers so you can adjust to sudden changes.
- Keep a fan or portable heater handy.
- Track your symptoms with a temperature diary to notice patterns—especially useful if tied to menstrual cycles, certain foods, or times of the day.
Final Thoughts: When to Take Fluctuating Body Temperature Seriously
Experiencing frequent shifts in body temperature can be frustrating, confusing, and at times, downright scary—especially when standard thermometers read “normal.”
But here’s the truth:
Most of the time, these fluctuations are not dangerous. They’re often linked to hormones, nervous system imbalances, medications, or lifestyle triggers.
However, persistent or extreme symptoms—especially when paired with fatigue, dizziness, weight changes, or pain—may point to something deeper. Whether it’s thyroid issues, electrolyte deficiencies, or chronic infections, don’t ignore the signals your body sends.
Bottom line?
Listen to your body. Track what you feel. And don’t hesitate to seek support.
Quick Recap: What You Can Do Today
- Stay hydrated and balance your electrolytes (magnesium, potassium).
- Support your nervous system with rest, gentle movement, and stress reduction.
- Assess lifestyle triggers like caffeine, alcohol, poor sleep, and heavy medications.
- Layer up, log symptoms, and consider seeing a healthcare provider if things persist.
Your body wants balance. Sometimes it just needs a little help finding it again.