If your baby has a fever, the single most important factor is age. A rectal temperature of 100.4°F (38°C) or higher in a baby younger than 3 months old requires an immediate call to your pediatrician, regardless of any other symptoms. For older babies, fever is usually manageable at home with comfort measures, fluids, and close monitoring.
What Counts as a Fever by Age
A fever in a baby is a rectal temperature of 100.4°F (38°C) or higher. The urgency depends on how old your baby is:
- Under 3 months: Any fever of 100.4°F or higher needs a call to your doctor right away, even if your baby seems fine otherwise. Young infants can’t fight infections the way older babies can, and a fever at this age sometimes signals something serious that needs testing.
- 3 to 6 months: Call your doctor if the temperature reaches 100.4°F or higher, or if your baby seems unusually irritable, sluggish, or uncomfortable even with a lower temperature.
- 6 to 24 months: A fever above 101°F (38.3°C) that lasts longer than one day without other concerning symptoms warrants a call. If your baby is acting reasonably normal, eating, and staying hydrated, you can often manage the fever at home while keeping a close eye on things.
How to Take an Accurate Temperature
For babies under 3 months, a rectal thermometer is the most accurate method available. Forehead (temporal) thermometers work reasonably well for babies 3 months and older, but if you get a borderline reading on a sick baby, confirming with a rectal temperature gives you the most reliable number. Ear thermometers aren’t considered accurate until after 6 months of age. Armpit readings are the least reliable of all methods and are best used as a quick first check rather than a definitive answer.
When you call your pediatrician, they’ll want to know the exact number and which method you used. A rectal reading removes the guesswork.
Comfort Measures That Actually Help
Dress your baby in one layer of lightweight clothing. It’s tempting to pile on blankets when your baby has chills, but bundling up can trap heat and push the fever higher. For sleep, one lightweight blanket is enough. Keep the room at a comfortable temperature, and use a fan if the room feels stuffy.
A lukewarm sponge bath can help bring a fever down, but it works best when combined with fever-reducing medicine. On its own, the temperature tends to bounce right back up after the bath. Never use cold water, ice, or rubbing alcohol. These can cause shivering, which actually raises your baby’s core temperature.
Offer frequent feedings. Babies with fevers lose fluids faster than usual, so breast milk, formula, or (for babies over 6 months) small sips of water are important. You don’t need to force large amounts at once. Smaller, more frequent feeds are easier for a feverish baby to tolerate.
When to Use Fever-Reducing Medicine
Acetaminophen (Tylenol) can be given to babies, but for children under 2 years, check with your doctor before giving it. The liquid form comes in a concentration of 160 mg per 5 mL, and dosing is based on your baby’s weight, not age. Give it every 4 hours as needed, but no more than 5 doses in 24 hours. Always use the dosing syringe that comes with the medicine rather than a kitchen spoon.
Ibuprofen (Advil, Motrin) is not safe for babies under 6 months. After 6 months, it can be used, but check with your doctor first for babies under 2 years or those weighing less than 12 pounds. Like acetaminophen, dosing is based on weight.
The goal of fever medicine isn’t necessarily to bring the temperature back to normal. Fever is part of your baby’s immune response. The real purpose is to help your baby feel comfortable enough to rest, eat, and stay hydrated.
Watch for Signs of Dehydration
Fever speeds up fluid loss, so dehydration is one of the most practical risks to monitor at home. For infants, fewer than six wet diapers in a day is a sign of mild to moderate dehydration. Other early signs include a dry mouth, fewer tears when crying, less playfulness than usual, and a sunken soft spot on top of the head.
Severe dehydration looks different. Your baby may become excessively sleepy or very fussy, have sunken eyes, cool or discolored hands and feet, or wrinkled skin. At this stage, your baby may only have one or two wet diapers in a full day. Severe dehydration needs medical attention quickly.
Red Flags That Need Immediate Attention
Beyond the age-based temperature thresholds, certain behaviors and symptoms signal that something more serious may be going on. Call your doctor or seek emergency care if your baby:
- Is unusually limp or listless: A baby who is overly quiet, difficult to wake, or seems “floppy” is more concerning than one who is fussy and crying.
- Is inconsolable: Crying is normal with a fever. Crying that cannot be soothed by holding, feeding, or any comfort measure is a warning sign.
- Has trouble breathing: Rapid breathing, flaring nostrils, or grunting with each breath all need prompt evaluation.
- Develops a rash that doesn’t fade when pressed: Tiny red or purple spots (petechiae) that stay visible when you press a glass against the skin can indicate a serious infection.
- Still looks very sick after the fever comes down: If your baby’s temperature drops but they still seem lethargic or unwell, that’s a sign that the underlying illness may need medical evaluation.
For any baby under 28 days old, a fever is treated as an emergency regardless of how well the baby appears to be acting. At this age, doctors typically run blood, urine, and sometimes spinal fluid tests to rule out bacterial infections.
What to Do if Your Baby Has a Seizure
Febrile seizures are triggered by a rapid rise in body temperature and affect a small percentage of children between 6 months and 5 years. They look alarming: your baby may shake, twitch, go stiff, moan, or lose consciousness. Most febrile seizures stop on their own within a few minutes and do not cause lasting harm.
If it happens, place your baby gently on the floor or ground, away from hard or sharp objects. Turn them onto their side to prevent choking. Loosen any clothing around the head and neck. Do not put anything in your baby’s mouth. Watch for any bluish color in the face, which could signal a breathing problem. Try to note how long the seizure lasts. If it goes beyond 5 minutes, call emergency services.
Even if the seizure stops quickly, call your pediatrician afterward. A first febrile seizure always warrants a medical evaluation to confirm the cause.