Recurring chills usually mean your body is trying to generate heat, either because something has lowered your actual temperature or because your brain’s internal thermostat has been reset by illness, hormonal shifts, or other triggers. The sensation itself is straightforward: your brain detects a gap between where your body temperature is and where it thinks it should be, then fires signals to your muscles to contract rapidly and produce warmth. But when chills keep coming back, the underlying cause matters more than the shivering itself.
How Your Body Creates Chills
A small region at the front of your brain called the preoptic area acts as your body’s thermostat. It constantly receives temperature readings from sensors in your skin and internal organs. When those readings fall below the target temperature, it sends a cascade of signals down through the brainstem and spinal cord that activate your skeletal muscles in short, involuntary bursts. That’s shivering. At the same time, blood vessels near the skin’s surface constrict to trap heat in your core, and tiny muscles at the base of your hair follicles contract, producing goosebumps.
This system is remarkably sensitive. It responds not just to actual cold but to anything that convinces the brain the body needs to be warmer, including infections, stress hormones, and metabolic changes. That’s why you can get chills sitting in a warm room.
Infections and Fever
The most common reason for sudden, repeated chills is that your immune system is fighting something. When your body detects a pathogen, immune cells release signaling molecules called cytokines. These molecules travel to the brain and effectively turn up the thermostat, raising the target temperature. Your brain then perceives your normal 98.6°F body as too cold and triggers shivering to close the gap. This is why chills typically come just before a fever rises, and why you feel freezing even while your temperature is climbing.
The chills stop once your body temperature catches up to the new, higher set point. When the infection is controlled and cytokine levels drop, the thermostat resets back down, and you start sweating to shed the excess heat. If you keep getting waves of chills over several days, it may mean your body is fighting a persistent or recurring infection, from a lingering virus to something like a urinary tract infection that hasn’t fully cleared.
Anxiety and Stress
Adrenaline can trigger chills even when you’re not sick. During a panic attack or a period of intense anxiety, your nervous system activates the same fight-or-flight pathways that constrict blood vessels near the skin. This pulls warm blood away from your extremities and toward your organs, making you feel suddenly cold and shaky. Piloerection (goosebumps) often comes along for the ride.
If you’re chronically stressed or dealing with an anxiety disorder, these episodes can recur frequently. They’re sometimes mistaken for signs of illness, which can increase anxiety further. The chills themselves aren’t dangerous, but they can be one of several physical symptoms that make anxiety feel like a medical emergency.
Low Thyroid Function
Your thyroid gland produces hormones that regulate how every cell in your body uses energy, including how much heat you generate. When the thyroid is underactive, a condition called hypothyroidism, your basal metabolic rate drops. You burn less fuel at rest, which means you produce less body heat. The result is a persistent feeling of being cold, often accompanied by fatigue, dry skin, and unexplained weight gain.
Hypothyroidism develops gradually, so you might not notice it at first. But if you find yourself reaching for a sweater when everyone else is comfortable, or getting chills in situations that never used to bother you, it’s worth having your thyroid levels checked with a simple blood test.
Iron Deficiency and Anemia
Iron plays a surprisingly central role in temperature regulation. When you’re iron-deficient, your blood carries less oxygen from your lungs to your tissues. That reduction in oxygen availability directly inhibits two key warming mechanisms: the constriction of blood vessels near the skin (which conserves heat) and the increase in metabolic rate (which generates heat). Your muscles also struggle to produce energy efficiently because iron-containing enzymes needed for cellular fuel production aren’t working at full capacity.
Iron deficiency also disrupts thyroid function. Without adequate iron, your body can’t properly convert thyroid hormones into their active form, which further lowers heat production. Research on iron-deficient animals shows they lose the ability to maintain normal body temperature in cold environments, and correcting the anemia restores normal thyroid responses. In practical terms, if you’re frequently cold and also experiencing fatigue, dizziness, or pale skin, iron-deficiency anemia could be connecting all of those symptoms.
Blood Sugar Drops
Low blood sugar triggers its own version of chills. When glucose levels fall below about 70 mg/dL, your body releases stress hormones to mobilize stored energy. These hormones cause shakiness, sweating, and a cold, clammy feeling that can mimic or overlap with true chills. For people with diabetes, this can happen when medication lowers blood sugar too aggressively or when meals are delayed.
There’s also a condition called idiopathic postprandial syndrome, where people experience symptoms of low blood sugar two to five hours after eating, even though their blood sugar isn’t actually low by standard measures. Shaking, chills, clamminess, and dizziness after meals are hallmarks. If your chills tend to follow a pattern around eating, this is worth paying attention to.
Hormonal Shifts
During perimenopause and menopause, fluctuating estrogen levels destabilize the brain’s temperature control. Most people associate this with hot flashes, but chills are part of the same disruption. A hot flash dilates blood vessels and causes a rush of heat and sweating. As that episode ends, the rapid heat loss can leave you shivering. Some people experience chills on their own, without a noticeable hot flash beforehand. Each episode typically lasts one to five minutes and can include sweating, chills, and anxiety in rapid succession.
These episodes can happen dozens of times a day or only a few times a week, and they may persist for years. They’re not exclusive to menopause either. Any major hormonal transition, including certain phases of the menstrual cycle, postpartum changes, or thyroid fluctuations, can temporarily unsettle your thermoregulation.
Less Obvious Triggers
Sleep deprivation lowers your core body temperature slightly, which can make you more prone to chills during the day. Dehydration reduces blood volume, making it harder for your body to distribute heat evenly. Even being significantly underweight can reduce the insulating fat layer and lower metabolic heat production enough to cause frequent chills.
Some medications also interfere with temperature regulation. Beta-blockers slow your heart rate and can reduce circulation to your extremities. Certain antidepressants and antipsychotics affect the brain’s thermoregulatory pathways. If your chills started around the time you began a new medication, that connection is worth exploring with whoever prescribed it.
Patterns That Help Identify the Cause
Paying attention to when your chills happen narrows down the possibilities considerably. Chills that come with body aches and fatigue point toward infection. Chills that arrive during stressful moments or alongside a racing heart suggest an anxiety-driven response. Chills that are constant, low-grade, and worst in your hands and feet align with thyroid or iron problems. Chills that follow meals, especially with shakiness, point toward blood sugar regulation.
If your chills are occasional and short-lived, they may simply reflect a drafty room or not eating enough that day. But chills that keep recurring over weeks, especially alongside other symptoms like fatigue, weight changes, or mood shifts, generally reflect something your body is trying to tell you about a deeper imbalance.