A high fever in adults is generally considered anything above 103°F (39.4°C), while in young children (3 months to 3 years), it starts at 101.3°F (38.5°C). Most fevers resolve on their own within a few days and signal that your immune system is actively fighting an infection. But a high fever requires active management to keep you comfortable, prevent dehydration, and avoid complications.
Know Your Temperature Thresholds
Fever thresholds vary by age, which matters when deciding how aggressively to respond. For children older than 3 years and adults, a reading above 99.9°F (37.7°C) counts as a fever, and above 103°F (39.4°C) is considered high. For babies between 3 and 36 months, a fever starts at 99.6°F (37.6°C) and becomes high at 101.3°F (38.5°C). These distinctions are important because younger children are more vulnerable to the effects of fever and need attention at lower temperatures.
For infants under 3 months, any fever at all is a reason to call your pediatrician immediately. Babies this young don’t have fully developed immune systems, and a fever can indicate a serious infection that needs prompt evaluation. For babies 3 to 6 months old, a temperature above 100.4°F (38°C) also warrants a call, especially if the baby seems unusually fussy or lethargic.
Stay Hydrated
Fever increases fluid loss through sweating and faster breathing. Dehydration can set in quickly, especially in children and older adults, and it will make you feel significantly worse. Water is the simplest option, but broth, diluted juice, and electrolyte drinks all help replace lost fluids and minerals. Sip consistently throughout the day rather than trying to drink large amounts at once, which can trigger nausea.
For babies under 1 year, use an oral rehydration solution like Pedialyte, which contains a balanced mix of water and salts designed for small bodies. Pedialyte ice pops can work well for toddlers who resist drinking.
Use Fever-Reducing Medication Carefully
Acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) are the two standard options for bringing a fever down. For adults, the maximum safe dose of acetaminophen is 4,000 milligrams in 24 hours. Going over that limit risks serious liver damage, and it’s easier to exceed than you’d think since acetaminophen is an ingredient in many combination cold and flu products.
You may have heard advice about alternating acetaminophen and ibuprofen every few hours. The American Academy of Pediatrics recommends against routinely doing this, particularly in children. The practice creates a complicated dosing schedule that increases the risk of accidentally giving too much of one or both medications. More than half of parents give an incorrect dose of these common pain relievers, partly because the over-the-counter label creates a false sense of safety. There’s also a theoretical risk that combining both drugs could stress the liver and kidneys. Stick with one medication at its recommended dose unless a doctor specifically advises otherwise.
For children under 2, don’t give acetaminophen without a doctor’s guidance. Children under 12 should not take extra-strength (500 mg) products. Liquid acetaminophen for kids comes as 160 mg per 5 mL, and children under 12 can take it every 4 hours, with a maximum of 5 doses in 24 hours. Always dose by your child’s weight, not age, and use the measuring device that comes with the medication rather than a kitchen spoon.
Keep Your Environment Comfortable
Dress in light, breathable clothing and keep your home at a normal, comfortable temperature. Resist the urge to pile on blankets, even if you have chills. Bundling up traps body heat and can push your temperature higher. A single light sheet or blanket is enough if you feel cold. Once the chills pass and you start sweating, remove even that layer.
Lukewarm sponging can help bring a fever down, but the water should be at room temperature, not cold. Cold water causes shivering, which actually raises your core temperature and makes you more uncomfortable. Studies on children treated with cold sponging found that about a third cried during the process and a quarter developed shivering. If sponging makes you or your child miserable, it’s doing more harm than good. Skip the ice baths and never use rubbing alcohol on the skin, which can be absorbed and cause poisoning.
Rest and Let the Fever Work
A fever is not a disease. It’s your body deliberately raising its internal thermostat to create an environment that’s hostile to viruses and bacteria. That process takes energy, which is why you feel wiped out. Rest is not optional. Cancel your plans, stay home, and sleep as much as your body wants. Pushing through a high fever slows recovery and increases the risk of spreading whatever infection is causing it.
You don’t necessarily need to eliminate the fever entirely. The goal of medication and cooling measures is to bring you from miserable to functional, not to hit a perfect 98.6°F. A temperature of 100 or 101 after taking medication is fine as long as you’re able to rest, drink fluids, and sleep.
When a Fever Needs Emergency Attention
Most fevers are caused by common viral infections and resolve within two to three days. But certain symptoms alongside a fever indicate something potentially serious. Go to the emergency room if a fever comes with any of the following:
- Stiff neck that resists movement, which can signal meningitis
- Confusion, altered speech, or difficulty waking up
- Seizures or convulsions
- Difficulty breathing
- A rash that looks like small bleeding spots under the skin
- Severe headache with sensitivity to light
- Persistent vomiting or significant abdominal pain
For children, call your pediatrician if a fever lasts longer than three days, or if a child between 7 and 24 months has a rectal temperature above 102°F (38.9°C) that persists beyond one day even without other symptoms. In adults, a fever above 103°F that doesn’t respond to medication, or any fever lasting more than three days, is worth a call to your doctor. A persistent fever sometimes points to a bacterial infection that needs antibiotics rather than just time.