Chills typically last anywhere from a few minutes to a couple of hours per episode, depending on what’s causing them. When they’re tied to an illness like the flu, you may experience repeated bouts of chills over two to three days, even though each individual episode is relatively brief. The total picture depends on the underlying cause, so the answer changes based on whether you’re fighting a virus, reacting to a vaccine, or dealing with something more serious.
Why Your Body Produces Chills
Chills happen because your brain’s internal thermostat, located in a region called the hypothalamus, has temporarily raised its target temperature. When you have an infection, your immune system releases chemicals that signal the hypothalamus to shift its set point upward. Your body then behaves as though its current normal temperature is too cold, even though it isn’t.
To close that gap, two things happen. Blood vessels near your skin constrict to keep heat from escaping, which is why your hands and feet feel cold. At the same time, your muscles start contracting rapidly (shivering) to generate heat. That shivering and cold sensation is what you experience as chills. Once your actual body temperature rises to match the new, higher set point, the chills stop. This is why chills tend to come at the beginning of a fever, not throughout it.
Chills From Colds and Flu
With the flu, symptoms generally appear one to four days after exposure and last five to seven days total. Chills tend to cluster in the first one to three days, when your fever is climbing or spiking. Each episode of shivering might last 20 to 30 minutes, but you can have several rounds in a single day as your temperature fluctuates. Once the fever stabilizes or breaks, chills usually stop.
Common colds produce milder fevers (if any), so chills are less intense and shorter-lived. You might feel a wave of chills for a few minutes here and there on the first day or two, but it’s rarely the teeth-chattering kind you get with the flu.
Chills After Vaccination
Post-vaccine chills are one of the most common side effects across many types of vaccines, including flu, COVID, pneumococcal, and meningococcal shots. According to the CDC, these side effects are generally minor and resolve within a few days. In practice, most people who get chills after a vaccine notice them starting 6 to 12 hours after the shot, peaking overnight or the next morning, and fading within 24 to 48 hours. The chills tend to be milder and shorter-lived than those caused by an actual infection.
Rigors: When Chills Are More Intense
A rigor is a more severe version of chills, involving uncontrollable, visible shaking rather than just feeling cold. Rigors almost always accompany a significant fever. The shaking happens because your muscles are contracting forcefully to drive your body temperature up quickly. A single rigor episode typically lasts 10 to 30 minutes, though it can feel much longer when you’re in the middle of one.
Rigors are more common with bacterial infections (like urinary tract infections, pneumonia, or kidney infections) than with ordinary colds. They can also occur with malaria, abscesses, and certain bloodstream infections. If you’re having repeated episodes of intense shaking chills, that pattern is worth paying attention to, as it often signals something beyond a routine virus.
Chills Without a Fever
Not all chills involve a fever. Hypothermia (a core body temperature below 95°F) causes shivering as the body tries to warm itself, and in that case the chills will continue until you’re warmed up. Anxiety, low blood sugar, and thyroid problems can also trigger chills without any infection. These episodes are usually shorter, lasting minutes rather than hours, and they resolve once the trigger is addressed.
How to Manage Chills at Home
The instinct to pile on blankets when you’re shivering is understandable, but overdoing it can trap too much heat once your fever peaks. A better approach:
- Wear loose, comfortable clothing. One or two layers is enough. Avoid bundling up heavily.
- Keep the room at a moderate temperature. You don’t want it too warm, but don’t try to make yourself cold either.
- Stay hydrated. Water is the best choice. Drink enough that your urine stays light yellow. Avoid alcohol, which worsens dehydration.
- Rest. Your body is burning extra energy generating heat, so give it a break.
- Use a fever reducer if needed. Acetaminophen or ibuprofen can lower the thermostat set point, which shortens the duration of chills by reducing the gap your body is trying to close.
Signs That Chills Need Medical Attention
Chills that come and go over a day or two with a mild virus are normal. But certain patterns warrant a call to your doctor or a visit to urgent care:
- Chills lasting more than 48 to 72 hours without improvement, especially with a persistent high fever
- Pain or burning when you urinate, which could point to a kidney or bladder infection
- Stiff neck combined with fever and chills, which can indicate meningitis
- Shortness of breath, chest pain, or confusion alongside chills
- Redness, swelling, or warmth in one specific area, suggesting a localized infection
Children under 5, adults over 65, and anyone with a chronic health condition should be evaluated promptly when chills and fever develop together, since their risk of complications is higher. If your body temperature drops below 95°F rather than rising, that’s hypothermia, and your organs can’t function properly at that temperature.