Chills are your body’s way of generating heat, usually because something has shifted your internal thermostat. Most often they signal an infection and rising fever, but chills can also result from cold exposure, low blood sugar, emotional stress, hormonal changes, or even a powerful piece of music. Understanding the cause behind your chills helps you figure out whether they’re routine or worth paying attention to.
How Your Body Produces Chills
A region deep in your brain called the hypothalamus acts as your body’s thermostat. When it senses that your core temperature is below its target, it activates a motor center that triggers rapid, involuntary skeletal muscle contractions. That’s the shivering you feel. Each tiny contraction generates a small amount of heat, and together they can raise your body temperature surprisingly fast.
This system works the same way whether you’re standing outside on a cold day or fighting off the flu. The difference is what moved the thermostat’s target in the first place.
Chills With Fever: The Most Common Cause
When bacteria, viruses, or other pathogens enter your body, your immune system releases signaling molecules that travel to the hypothalamus. These molecules trigger the production of a chemical called prostaglandin E2, which effectively raises your brain’s temperature set point. Your normal 98.6°F suddenly feels “too cold” to your thermostat, so your body starts shivering to close the gap. That’s why you can feel freezing and want to pile on blankets even as a thermometer shows your temperature climbing.
Once the fever peaks and the set point resets back to normal, the process reverses. Now your body is “too hot,” and you start sweating to cool down. This cycle of chills followed by sweating is a hallmark of fever from infections like the flu, COVID, urinary tract infections, and pneumonia.
Chills vs. Rigors
Not all chills feel the same. A mild chill might just be a light shivery sensation under your skin. A rigor is something different: severe, violent shaking that you can’t control, often accompanied by a high fever. Rigors tend to signal a more serious infection.
Research on shaking chills and bloodstream infections found that rigors are a highly specific predictor of bacteremia, meaning bacteria in the blood. In a large analysis of nearly 49,000 patients, shaking chills had 87% specificity for bacteremia. That means when someone has true rigors, there’s a meaningful chance bacteria have entered the bloodstream. However, only about 37% of people with bacteremia actually experience shaking chills, so the absence of rigors doesn’t rule out a serious infection.
Chills Without Fever
Plenty of conditions cause chills with no fever at all. Some of the most common include:
- Low blood sugar (hypoglycemia): When blood glucose drops too low, particularly in people with diabetes, the body releases stress hormones that can trigger shivering and a cold, clammy feeling.
- Menopause: Hot flashes and night sweats often come paired with chills as your body overshoots its cooling response, leaving you shivering after the flush passes.
- Panic attacks and acute stress: A surge of adrenaline can cause trembling and chills. People sometimes experience this after a traumatic event like a car accident, and it can recur in conditions like PTSD.
- Anesthesia: As many as two in three people experience chills and shivering after receiving general anesthesia for surgery, partly because the body cools during the procedure.
- Alcohol hangover or drug withdrawal: Both can destabilize your body’s temperature regulation and trigger shivering.
- Certain cancers: Blood cancers like leukemia can cause recurring chills, sometimes with night sweats and unexplained weight loss.
Emotional and Musical Chills
If you’ve ever gotten goosebumps from a song, a speech, or a movie scene, that’s a real physiological phenomenon called frisson. It happens in your brain’s reward system: the anticipation of a musical peak activates one reward region, and the moment of emotional release activates another. Both areas release dopamine, the same chemical involved in pleasure from food or social connection.
Brain imaging studies show that frisson involves a whole network of regions working together, including areas responsible for emotion, memory, and physical arousal. People who experience it more intensely tend to have stronger neural connections between their auditory processing areas and their emotional and reward centers. It’s harmless and, for most people, genuinely enjoyable.
Cold Exposure and Hypothermia
Shivering from cold is the most straightforward version of chills. Your core temperature drops, and your hypothalamus responds by making your muscles contract to generate warmth. In mild hypothermia, when core temperature falls to between 90 and 95°F, shivering is often accompanied by fatigue, nausea, and pale skin.
Here’s the critical detail: shivering typically stops when your core temperature reaches about 86 to 90°F. That’s not a good sign. It means your body has exhausted its ability to warm itself, and severe hypothermia is setting in. If someone who was shivering in the cold suddenly stops and seems confused or drowsy, that’s a medical emergency.
Medication-Related Chills
Certain medications can trigger chills or full rigors as a side effect, particularly drugs given by IV infusion. Some cancer treatments are well-documented triggers. One commonly used antibody therapy causes rigors in 13% to 33% of patients, while another immune-suppressing drug triggers them in roughly 55% of patients. Certain antifungal medications are also known for causing infusion-related shaking. If you develop chills during or shortly after an IV treatment, it’s a recognized reaction that medical staff can manage in real time.
Chills in Children
Children experience chills for the same reasons adults do, but fevers in young kids carry an additional concern: febrile seizures. These seizures typically happen in the first few hours of a fever, during the initial rapid rise in temperature, which is exactly when chills are most intense. They’re most common between 6 months and 5 years of age, with the highest risk between 12 and 18 months.
Febrile seizures are frightening to witness but are usually brief and don’t cause lasting harm. The chills themselves don’t cause the seizure. It’s the speed of the temperature spike that matters.
When Chills Signal Something Serious
Most chills resolve on their own or with treatment of the underlying cause. But certain patterns deserve prompt medical attention. Rigors with a high fever, especially if you also have a rapid heart rate, confusion, or feel much sicker than a typical cold would explain, can point to a bloodstream infection or sepsis. Recurring chills with unexplained weight loss or drenching night sweats can be a sign of cancer or chronic infection. And as noted above, shivering that suddenly stops in someone exposed to severe cold is a warning sign of dangerous hypothermia.
For the everyday chill that comes with a cold or flu, the shivering is uncomfortable but doing exactly what it’s supposed to do: helping your body fight off the infection by raising its temperature to a level less hospitable to pathogens.