Most fevers resolve on their own within a few days, and the right combination of rest, fluids, and simple medications can make you much more comfortable while your body fights off the underlying cause. A fever is generally defined as a body temperature above 100.4°F (38°C), and chills are part of the same process: your brain’s thermostat has temporarily reset to a higher temperature, and your body shivers to generate the heat needed to reach that new set point.
Why Fever and Chills Happen Together
Your hypothalamus, the part of the brain that regulates body temperature, normally keeps you around 98.6°F. When your immune system detects an infection, it sends chemical signals that push that set point higher. Your body then acts as though it’s too cold: blood vessels near the skin constrict to trap heat, and your muscles start shivering to produce more warmth. That’s why you feel freezing and pile on blankets even though your actual temperature is climbing. Once your blood temperature reaches the new, higher set point, the chills typically stop, and you may start feeling hot instead.
This process is uncomfortable, but it serves a purpose. Many bacteria and viruses reproduce less efficiently at higher temperatures, and certain immune cells work better when the body is slightly warmer. So a mild to moderate fever is your immune system doing its job.
Keeping Comfortable With Rest and Cooling
Physical activity raises your body temperature further, so genuine rest (not just sitting on the couch answering emails) is important. Lie down, sleep when you can, and let someone else handle meals and childcare if possible.
Once the chills pass and your temperature is elevated, shift your environment to help your body release heat. Dress in light, breathable clothing rather than heavy layers. Keep the room cool, and sleep with just a sheet or a light blanket. A lukewarm (not cold) washcloth on your forehead or the back of your neck can also help. Avoid ice baths or very cold water, which can trigger more shivering and actually push your core temperature higher.
During the chills phase, it’s fine to use a blanket to stop the shaking. Just switch to lighter coverings once the shivering stops and you start feeling warm.
Staying Hydrated
Fever increases fluid loss through sweating, faster breathing, and higher metabolic activity. Normal daily water needs run about 25 to 30 milliliters per kilogram of body weight, so a 150-pound person needs roughly 1.7 to 2 liters a day under normal conditions. With a fever, you need more than that.
Water is the simplest option, but you’re also losing electrolytes (sodium, potassium, chloride) through sweat. Oral rehydration solutions, diluted sports drinks, or broth-based soups help replace both fluid and minerals. Herbal teas and popsicles count toward your intake too, and they may be easier to tolerate if your stomach is sensitive. Avoid alcohol and large amounts of caffeine, both of which can increase dehydration.
A practical way to monitor hydration: check your urine color. Pale yellow means you’re on track. Dark yellow or amber means you need more fluids.
Over-the-Counter Fever Reducers
Two widely available medications lower fever effectively: acetaminophen (Tylenol) and ibuprofen (Advil, Motrin). They work through different pathways, so you can use either one or alternate between them if a single medication isn’t providing enough relief.
For adults, acetaminophen is typically dosed at 500 to 1,000 mg every four to six hours, with a maximum of 3,000 to 4,000 mg per day depending on the product. Ibuprofen runs 200 to 400 mg every six to eight hours, with a daily over-the-counter maximum of 1,200 mg. Always check the label, because many cold and flu combination products already contain acetaminophen, and doubling up without realizing it is a common mistake that can strain the liver.
You don’t have to take a fever reducer if your temperature is only mildly elevated and you feel okay. These medications treat the discomfort, not the infection itself. If the fever is making it hard to sleep, eat, or stay hydrated, that’s when medication helps most.
For Children
Children’s doses are based on weight, not age. Use the dosing chart on the product packaging or a pediatric weight-based calculator, and always use the measuring device that comes with the medication rather than a kitchen spoon. Never give aspirin to children or teenagers with a fever, as it’s linked to a rare but serious condition called Reye’s syndrome.
What to Eat When You Have a Fever
Your body burns more calories when your temperature is elevated, but appetite often drops. Don’t force large meals. Focus on easy-to-digest foods that also deliver some fluid: soups, broths, yogurt, applesauce, toast, and rice. If you can’t eat much, prioritize fluids and electrolytes over solid food. Your appetite will return as the fever breaks.
Temperature Thresholds That Need Attention
Not every fever can be safely managed at home. The guidelines vary by age, and they’re worth knowing before you need them.
- Babies under 3 months: Any fever at or above 100.4°F (38°C) needs immediate medical evaluation, regardless of how the baby seems otherwise.
- Babies 3 to 6 months: A rectal temperature above 102°F (38.9°C) warrants a call to your pediatrician. Call sooner if the baby seems unusually irritable, sluggish, or uncomfortable even at lower temperatures.
- Children 7 to 24 months: A rectal temperature above 102°F that lasts more than one day without other symptoms should be evaluated. A fever lasting longer than three days at any temperature also needs a medical check.
- Adults: Call your doctor if your temperature reaches 103°F (39.4°C) or higher, or if a lower fever persists for more than three days.
Warning Signs That Need Immediate Care
Certain symptoms alongside a fever suggest something more serious than a typical viral infection. For adults, seek immediate medical attention if a fever comes with any of the following: severe headache, stiff neck (especially pain when bending the head forward), mental confusion or altered speech, persistent vomiting, difficulty breathing or chest pain, a new rash, unusual sensitivity to bright light, abdominal pain, pain when urinating, or seizures.
For children, the red flags include listlessness, poor eye contact, repeated vomiting, severe headache, or a seizure. If a child has a seizure lasting more than five minutes, call 911. Any fever that develops after a child has been left in a hot car requires emergency care immediately.
How Long a Typical Fever Lasts
Most fevers caused by common viral infections (colds, flu, stomach bugs) peak within the first day or two and resolve within three to four days. You may notice a pattern where the temperature rises in the late afternoon and evening and drops by morning. This is normal and doesn’t mean the infection is getting worse.
Once the underlying infection is under control, the hypothalamus resets back to its normal set point. At that point, you may experience heavy sweating as your body works to shed the extra heat. This “breaking” of the fever is a sign of improvement. Keep drinking fluids through this phase, as the sweating can be significant. If the fever returns after being gone for a full day or two, or if new symptoms develop, that’s worth a call to your doctor since it could signal a secondary infection or a different underlying cause.