Recurring chills happen when your brain’s temperature control center repeatedly triggers muscle contractions to generate heat, either because your body is genuinely cold, fighting an infection, or responding to a hormonal, metabolic, or emotional signal that mimics cold exposure. If you keep getting chills without an obvious explanation like being in a cold room, something is pushing your internal thermostat to activate when it shouldn’t need to.
How Your Body Creates Chills
A small region at the front of your hypothalamus acts as your body’s thermostat. It constantly receives temperature data from sensors in your skin and compares it to the target temperature it wants to maintain. When those readings fall below the target, or when the target itself gets raised (as happens during a fever), the hypothalamus sends signals down through the brainstem to your spinal cord, which activates rapid, involuntary muscle contractions. That’s the shivering you feel.
This system has two modes. The first is straightforward: you’re actually cold, and your muscles contract to produce heat. The second is more relevant to recurring, unexplained chills. During infection, inflammatory signals cause the production of a compound called prostaglandin E2 inside the hypothalamus. This compound essentially tricks your thermostat into raising its set point, so your body “thinks” it’s too cold even when your actual temperature is normal. The result is chills, shivering, and that deep feeling of being cold from the inside out, sometimes before a fever ever appears.
Infections and Immune Responses
The most common reason for sudden or recurring chills is your immune system responding to an infection. Viral infections like the flu, COVID-19, and common colds all trigger the prostaglandin pathway that resets your thermostat upward. You may feel intense chills hours before a measurable fever develops, or you might get waves of chills that come and go as your immune system ramps up and down over the course of an illness.
Bacterial infections, particularly urinary tract infections and respiratory infections, can also cause recurring episodes of shaking chills called rigors. These tend to be more intense than viral chills and often accompany spikes in fever. If you’re getting repeated bouts of chills over days or weeks without a clear cold or flu, a lingering or undertreated infection is one of the first things worth investigating.
Thyroid Problems and Metabolism
Your thyroid gland controls how much heat your body generates at rest. When it underperforms (hypothyroidism), your baseline heat production drops, and you become unusually sensitive to cool temperatures that wouldn’t bother most people. This isn’t just feeling chilly. Research published in the Journal of the Endocrine Society found that even patients with treated hypothyroidism had measurably lower hand temperatures compared to healthy controls, suggesting their bodies still struggled to maintain warmth despite medication.
The issue comes down to a conversion problem. Your thyroid produces a relatively inactive hormone (T4) that needs to be converted into an active form (T3) to drive heat production. In people with hypothyroidism, this conversion is often impaired, which means the cells responsible for generating warmth, particularly muscles and brown fat tissue, don’t get the signal to fire up. If your recurring chills come with fatigue, weight gain, dry skin, or sluggish thinking, an underactive thyroid is a strong possibility. A simple blood test can confirm it.
Low Blood Sugar
When your blood sugar drops below about 70 mg/dL, your body releases a surge of stress hormones, primarily adrenaline, to mobilize stored energy. That adrenaline rush produces a distinctive cluster of symptoms: shaking, sweating, a racing heart, dizziness, and chills. The chills from low blood sugar often feel different from infection-related chills because they come with a simultaneous cold sweat and a sense of anxious urgency.
If your chills tend to hit when you’ve gone too long without eating, after intense exercise, or in the middle of the night, blood sugar dips are worth considering. This is especially relevant if you take diabetes medication, but it can also happen in people without diabetes who skip meals regularly or follow very low-carb diets. Eating something with both sugar and protein usually resolves the episode within 15 to 20 minutes.
Hormonal Shifts During Menopause
Hot flashes get most of the attention during menopause, affecting up to three out of four women. But some women experience cold flashes instead, or alternate between the two. These cold flashes produce sudden waves of chills, sometimes with visible goosebumps and shivering, and they can recur unpredictably for months or years during the menopausal transition.
The exact mechanism isn’t fully understood, but fluctuating estrogen levels appear to destabilize the hypothalamus’s temperature regulation, narrowing the range of temperatures your body considers “normal.” Small shifts that your brain would previously have ignored now trigger a full shivering response. If you’re in your 40s or 50s and your chills don’t line up with any illness or obvious trigger, hormonal changes are a likely explanation.
Anxiety and the Stress Response
Your fight-or-flight system can produce chills that feel identical to being cold, even when you’re in a warm room. During periods of high anxiety or a panic attack, your nervous system redirects blood away from your skin and toward your muscles and vital organs. Your skin temperature drops as a result, and your hypothalamus detects that drop and triggers shivering.
Anxiety-related chills tend to come in waves and often accompany other physical symptoms like a tight chest, shallow breathing, nausea, or a sense of dread. If your chills seem to appear during stressful situations, before important events, or alongside racing thoughts, your nervous system’s stress response is likely the culprit. Chronic stress and generalized anxiety can keep this system partially activated for extended periods, which explains why some people feel persistently chilly during high-stress phases of life.
Medications and Treatments
Certain medications can disrupt your body’s temperature regulation and cause recurring chills as a side effect. Cancer treatments are among the most common offenders. Chemotherapy drugs and biologic therapies, particularly immune-stimulating treatments like interferons, frequently cause flu-like symptoms including chills, sometimes severe enough to require medication to control the shivering itself.
Outside of cancer treatment, opioid withdrawal is notorious for producing intense, recurring chills. Some blood pressure medications, certain antidepressants, and drugs that affect hormone levels can also shift your thermoregulation enough to cause periodic chills. If your episodes started around the time you began a new medication, that timing is worth discussing with whoever prescribed it.
Signs That Need Prompt Attention
Most chills are harmless and resolve on their own, but certain combinations of symptoms signal something more serious. The Cleveland Clinic recommends contacting a healthcare provider if your chills occur alongside a temperature above 104°F or below 95°F, chest pain, difficulty breathing, severe abdominal pain, or extreme fatigue that doesn’t improve with rest. Chills paired with unexplained weight loss, drenching night sweats, or swollen lymph nodes also warrant investigation, as these combinations can point to infections, autoimmune conditions, or other systemic problems that need diagnosis rather than home management.
Chills that keep coming back over weeks without any obvious pattern, especially if they’re accompanied by fatigue or feeling generally unwell, are worth bringing up even if no single episode feels alarming. A basic workup including blood counts, thyroid levels, and inflammatory markers can usually narrow down or rule out the most common underlying causes.