If your baby is younger than 3 months and a rectal thermometer reads 100.4 F (38 C) or higher, call your pediatrician right now or go to an emergency department, and do not give fever medicine first. The American Academy of Pediatrics (AAP) treats fever at this age as a possible sign of serious infection that has to be checked in person. Past that age, the number matters far less than how your child drinks, breathes, plays, and responds to you.
The red lines, age by age
Under 3 months (12 weeks): a rectal temperature of 100.4 F (38 C) or higher means your baby gets seen now, day or night, and no fever medicine before the visit. Fever in the first 12 weeks can signal a serious infection, and your baby needs an in-person exam to decide what tests come next.
3 to 6 months: any fever earns a call to your pediatrician within 24 hours, and sooner if your baby is feeding poorly, unusually sleepy, or hard to console.
Over 6 months: watch the child, not the thermometer. The AAP's call-now triggers at any age: a temperature repeatedly above 104 F (40 C), or a child who still acts sick after the fever comes down. A child at 102 F who takes fluids and watches cartoons is in better shape than a child at 100.6 F who is limp and refusing to drink. Also call if a fever lasts more than 24 hours in a child under 2, or more than 3 days in an older child.
Fever is a symptom, and the number can mislead you
Fever is not the illness. It is the body's own defense at work, and the AAP's clinical report on fever states there is no evidence that fever by itself worsens the course of an illness or causes long-term neurologic damage. The goal of treatment is your child's comfort, not a normal reading on the thermometer.
Pediatricians have had a name for the panic since 1980: fever phobia. When Johns Hopkins researchers revisited it in 2001, 91 percent of caregivers believed fever could harm their child, 21 percent named brain damage, and 14 percent named death. One in four gave fever medicine for temperatures below 100 F, and 85 percent said they would wake a sleeping child to give it. That fear is what drives dosing mistakes at 3 a.m.
Dosing rules: weight, not age, and never from memory
Acetaminophen (Tylenol) and ibuprofen (Motrin, Advil) are dosed by your child's weight, not age. We do not print a dosing chart on purpose: concentrations and guidance change, and a stale chart is dangerous. Use the AAP's weight-based tables for acetaminophen and ibuprofen, and have your pharmacist confirm the dose and syringe markings for the exact product in your hand.
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Three hard rules. No ibuprofen for babies under 6 months. Ask your doctor before giving acetaminophen under age 2. Never give aspirin to a child or teen with a fever: aspirin taken during a viral illness is linked to Reye syndrome, a rare but life-threatening brain and liver emergency, which is why the National Institute of Neurological Disorders and Stroke (NINDS) points families to acetaminophen or ibuprofen instead.
If your pediatrician suggests alternating the two medicines, write down the drug, the dose, and the time, every single dose. The AAP warns that combination schedules make unsafe dosing more likely, and in the Hopkins study 44 percent of caregivers using ibuprofen were already giving it too often. A note on the nightstand beats memory in the dark.
Febrile seizures: what to do while one happens
Febrile seizures affect 2 to 5 percent of children between 6 months and 5 years, which makes them the most common seizure event of childhood. A simple febrile seizure, under 15 minutes and once in 24 hours, does not cause brain damage or long-term health problems, according to NINDS.
During the seizure: note the start time. Move your child to the floor and turn them onto their side. Do not restrain them, and never put anything in their mouth. Call 911 if the seizure passes 5 minutes, or if it stops sooner but your child is not coming around quickly. After any first febrile seizure, have your child seen promptly so the doctor can find the cause of the fever.
Fever with sickle cell disease is its own emergency
For a child with sickle cell disease, serious bacterial infections can develop fast, and fever may be the first sign. The National Heart, Lung, and Blood Institute (NHLBI) is unambiguous: a temperature above 101.3 F (38.5 C) means provider evaluation and antibiotics right away, and some children need hospital care. Do not wait to see whether the fever comes down; the fever itself is the emergency. Our guide to sickle cell disease in children covers the infection risk and the routine care that lowers it.
In the ER: how to be heard
The research says emergency departments do not always take Black parents at their word. In a national study of ER visits for appendicitis, about 21 percent of Black children received opioid pain medication, and among children in severe pain the authors concluded a different threshold for treatment was being applied to Black kids. A 2020 study of more than 21,000 ER visits for broken bones found the same pattern: the system gave Black children opioid pain relief less often and got their pain down to mild or none less often. That is a failure of the system, not of parents, and it is why you walk in prepared.
Four moves that change how a visit goes:
- Give the timeline in one sentence. "Fever started Tuesday, peaked at 103.9 last night, acetaminophen at 11 p.m. brought it to 101, and she stopped drinking this morning."
- Name the red flag you saw, in plain words. "There is a rash on her chest that does not fade when I press a glass against it."
- Before you leave, ask: "What exactly should change for us to come back?" Push for specifics: a temperature, a symptom, a number of hours.
- Ask for discharge instructions in writing, with those return criteria written on them.
What not to do tonight
- No alcohol baths or rubs, no ice baths, no cold sponging. The AAP says these are no longer recommended and can harm your child. In the Hopkins study, 18 percent of caregivers who sponged used alcohol.
- Do not bundle a feverish child in blankets to sweat it out. Comfort is the goal; one light layer.
- Do not wake a comfortably sleeping child to give fever medicine. A sleeping child is not uncomfortable, and comfort is the reason to dose.
- Do not dose from memory in the dark. Write down every dose: drug, amount, time.
How to get care
A pediatrician who knows your child before the sick night is the difference between a 2 a.m. phone call and a 2 a.m. waiting room. If you are looking for one, find a Black pediatrician through our provider directory. And for the fevers that come with ear pain, read our guide to ear infections in Black children.
Frequently asked questions
How high is too high for a child's fever? ▼
For a baby under 3 months, 100.4 F (38 C) rectal is the emergency line. For older children there is no single dangerous number: the AAP flags temperatures repeatedly above 104 F (40 C) and a child who looks very ill, will not drink, or still acts sick after the fever comes down.
When should I take my child to the ER for a fever? ▼
Go now for a stiff neck, trouble breathing, a rash that does not fade under a pressed glass, dehydration signs, a floppy or hard-to-wake child, a seizure, any fever in a baby under 3 months, or fever with sickle cell disease or a weakened immune system.
Do febrile seizures cause brain damage? ▼
No. Simple febrile seizures, under 15 minutes and once in 24 hours, do not cause brain damage or long-term health problems, per NINDS. Call 911 if a seizure lasts more than 5 minutes, and have any first seizure checked promptly.
Can I alternate Tylenol and Motrin for my child's fever? ▼
Only on your pediatrician's advice, and only with every dose written down: drug, amount, time. The AAP warns that combination schedules invite dosing errors. Both medicines dose by weight; use the AAP tables and confirm with your pharmacist.
Why is fever an emergency in a child with sickle cell disease? ▼
In sickle cell disease, serious bacterial infections can turn dangerous within hours, and fever may be the first sign. NHLBI guidance calls for immediate evaluation and antibiotics for a temperature above 101.3 F (38.5 C).