Body chills are involuntary muscle contractions that make you shiver, tremble, or feel cold even when your surroundings are warm. They’re one of the body’s built-in heating mechanisms, and while they most commonly signal the start of a fever, they can also stem from low blood sugar, emotional stress, certain medications, and other non-infectious causes.
How Your Body Produces Chills
Chills originate in the hypothalamus, a small region at the base of the brain that acts as your internal thermostat. When it detects that your body needs more heat, whether because of cold exposure or the onset of illness, it sends involuntary signals through the nervous system to your skeletal muscles. Those muscles contract rapidly and rhythmically, generating warmth through sheer physical effort. That’s the shivering you feel.
At the same time, your blood vessels near the skin’s surface constrict to keep heat from escaping. You may notice your hands and feet feel icy, your skin looks pale, or you get goosebumps. Your body also ramps up its metabolic rate to produce additional heat internally. All of these responses work together, and chills are simply the most noticeable part of the package.
Why Fever Triggers Chills
This is the part that confuses most people: if you have a fever, your body is already warm, so why would you feel cold? The answer is that during infection, your hypothalamus deliberately raises its temperature set point. It behaves as though 102°F is the new normal, which means your actual body temperature of 98.6°F now registers as “too cold.” Your brain responds the same way it would if you stepped outside in winter. It triggers shivering, drives you to seek blankets, and constricts blood flow to your skin, all in an effort to push your temperature up to that new, higher target.
Once your temperature reaches the elevated set point, the chills typically stop. Later, when the fever breaks and the set point drops back to normal, the opposite happens: you feel overheated and start sweating to cool down. A fever is medically defined as a body temperature of 100.4°F (38°C) or higher, though chills can begin even during a low-grade rise between 99.1°F and 100.4°F.
Chills vs. Rigors
Not all chills feel the same. Mild chills might involve light shivering and a general sense of being cold. Rigors are a more severe form: intense, uncontrollable shaking that can make your teeth chatter and your whole body tremble visibly. Rigors often accompany high fevers or serious infections and can last several minutes. They’re physically exhausting in a way mild chills are not, and they tend to signal a more significant immune response.
Common Causes Beyond Infection
Fever from a cold, flu, or other infection is the most familiar trigger, but plenty of other situations cause chills without any illness involved.
- Low blood sugar (hypoglycemia): When blood glucose drops too low, particularly in people with diabetes, the body releases stress hormones that can trigger trembling and chills alongside dizziness and sweating.
- Emotional stress and panic attacks: A surge of adrenaline during a panic attack, a traumatic event, or even an intense argument can produce shaking that feels identical to fever-related chills. People with PTSD sometimes experience this as a recurring symptom.
- Cold exposure: The most straightforward cause. If your core temperature starts dropping, your body shivers to generate heat.
- Medications: Certain cancer therapies are well known for causing flu-like symptoms that include chills. Biologic therapies such as interferons, colony-stimulating factors, and monoclonal antibodies frequently trigger this response. Several chemotherapy drugs do the same.
- Anesthesia recovery: Shivering after surgery is extremely common, as anesthesia disrupts your body’s temperature regulation.
When Chills Signal Something Serious
Most of the time, chills resolve on their own or once a mild illness passes. But chills combined with certain other symptoms can point to sepsis, a life-threatening response to infection that requires emergency care. Warning signs include a fast heart rate, rapid breathing, confusion, extreme weakness, low blood pressure, warm or clammy skin, and very high or very low body temperature. Sepsis can escalate quickly, so the combination of shaking chills with any of those symptoms warrants an immediate trip to the emergency room.
In infants, the threshold for concern is lower. Any fever at all in a baby younger than 3 months old warrants a call to a healthcare provider. For babies 3 to 6 months old, a temperature above 100.4°F or any signs of unusual sleepiness, floppiness, or persistent fussiness should prompt the same call. Between 6 and 24 months, a fever above 100.4°F that lasts more than a day needs medical attention.
Managing Chills at Home
If your chills are tied to a mild illness, the goal is comfort while your immune system does its work. Layer blankets until the shivering phase passes, but don’t bundle up so heavily that you overheat once the fever stabilizes. Drink plenty of fluids, since fever increases water loss through sweating and faster breathing. Warm beverages can help you feel warmer and keep you hydrated at the same time.
Over-the-counter fever reducers can lower the hypothalamic set point back toward normal, which addresses both the fever and the chills. If chills are caused by low blood sugar, eating or drinking something with fast-acting carbohydrates (juice, glucose tablets, a few crackers) will usually stop the shaking within 15 to 20 minutes. For chills driven by anxiety or panic, slow breathing techniques and removing yourself from the stressful situation help your nervous system calm the adrenaline response.
Chills that come back repeatedly without an obvious explanation, or that happen alongside unexplained weight loss, night sweats, or persistent fatigue, are worth bringing up with a doctor. These patterns sometimes point to underlying conditions that need further evaluation.