A baby has a fever when their temperature reaches 100.4°F (38°C) or higher. For most babies older than 3 months, you can safely manage a fever at home with lightweight clothing, extra fluids, and the right dose of fever-reducing medication. The approach depends on your baby’s age, because what’s routine for a 9-month-old can be a medical emergency for a newborn.
Check the Temperature Accurately First
Before you do anything else, get a reliable reading. A rectal thermometer is the most accurate method for babies, especially those younger than 3 months. Forehead (temporal artery) thermometers are nearly as accurate and work well for babies 3 months and older, though your pediatrician may still want a rectal confirmation if your baby looks sick.
Ear thermometers aren’t reliable until after 6 months of age. Armpit readings are the least accurate of all and should only be used as a quick first check. Skip forehead strips and color-changing pacifier thermometers entirely, as they’re not dependable enough to base decisions on.
Age Determines How Urgently You Should Act
A fever of 100.4°F in a 2-week-old is a completely different situation than the same temperature in a 10-month-old. Here’s how the thresholds break down:
- Under 3 months: Any fever of 100.4°F (38°C) or higher needs immediate medical attention. Do not give medication or try to manage it at home first. Call your pediatrician or go to the emergency room right away.
- 3 to 6 months: A fever of 102°F (38.9°C) or higher warrants a call to your doctor. Lower fevers can typically be managed at home while you monitor your baby closely.
- Over 6 months: Contact your doctor at 103°F (39.4°C) or higher, or if the fever persists for more than a day or two.
The reason newborns get special urgency is that their immune systems are immature. The American Academy of Pediatrics has detailed evaluation guidelines for babies 8 to 60 days old with fevers, which can include blood tests, urine samples, and sometimes a spinal fluid check. That sounds alarming, but it’s because young infants can deteriorate quickly from infections that older babies fight off easily. Getting evaluated fast is the single most important thing you can do for a feverish newborn.
Fever-Reducing Medication by Age
Acetaminophen (Tylenol) can be given to babies 8 weeks and older. Do not give it to any infant younger than 8 weeks. Ibuprofen (Motrin, Advil) is off-limits until 6 months of age unless your pediatrician specifically says otherwise. Always dose by your baby’s weight, not their age, since weight-based dosing is more accurate.
If one medication alone isn’t controlling the fever, you can alternate acetaminophen and ibuprofen every 3 hours for short-term relief (no longer than 24 hours of alternating). This works because the two medications lower fever through different mechanisms. Write down each dose and the time you gave it so you don’t accidentally double up. For babies under 6 months, talk to your pediatrician before trying an alternating schedule, since ibuprofen isn’t normally used at that age.
Home Cooling Methods That Actually Help
Medication is the most effective way to bring a fever down, but several non-medication strategies help alongside it.
Dress lightly. Put your baby in one layer of lightweight clothing and use a single light blanket for sleep. It’s tempting to bundle up a baby who has the chills, but extra layers trap heat and can push the fever higher. If the room feels hot or stuffy, a fan pointed away from the baby to circulate air is fine.
Try a lukewarm bath. A lukewarm sponge bath or tub bath can help lower body temperature, but it works best when paired with medication. Without medication, the fever tends to bounce right back up once the bath is over. Never use cold water, ice, or rubbing alcohol. Cold causes shivering, which actually raises the body’s core temperature and makes things worse. Alcohol rubs are dangerous for babies because alcohol can be absorbed through the skin.
Keep Your Baby Hydrated
Fever increases fluid loss, and babies dehydrate faster than adults. If you’re breastfeeding or formula feeding, offer feeds more frequently than usual. Babies don’t need water or electrolyte drinks if they’re under 6 months and still nursing or taking formula regularly. Older babies who eat solids can have small sips of water between feeds.
The clearest way to track hydration is by counting wet diapers. Fewer wet diapers than normal is an early warning sign. Other dehydration signals to watch for include crying without tears, a dry mouth or tongue, and in young babies, a sunken soft spot on the top of the head. If your baby hasn’t had a wet diaper in 8 hours, that’s a sign of significant dehydration and warrants a call to your doctor.
Warning Signs That Need Emergency Care
Most fevers in babies over 3 months are caused by common viral infections and resolve on their own within a few days. But certain symptoms alongside a fever signal something more serious. Get emergency help if your baby shows any of these:
- Lethargy: Your baby stares into space, won’t smile, won’t play, or is too weak to cry. This is different from being sleepy. A lethargic baby is hard to rouse and barely responds to you.
- Inconsolable crying: Nonstop crying that you can’t soothe, especially if your baby pulls away when held or moved. This often indicates severe pain.
- Trouble breathing: Fast breathing, grunting with each breath, or skin pulling in between the ribs. Bluish or gray lips, tongue, or gums mean your baby isn’t getting enough oxygen. Call 911.
- Dehydration signs: No wet diaper in 8 hours, no tears when crying, dry mouth, sunken soft spot.
- Bright green vomit: This can indicate a bowel obstruction and needs immediate evaluation.
- A stiff or tender belly: If pressing gently on your baby’s stomach causes them to wince or scream, something more serious may be going on.
For newborns under 1 month, the bar is even lower. Poor feeding, excessive sleepiness, vomiting, a change in skin color, or simply looking “off” in combination with a fever all warrant immediate medical evaluation. At that age, these symptoms are considered serious until proven otherwise.