A temperature of 100.4°F (38°C) or higher, taken rectally, is a fever in a 6-month-old. At this age, most fevers are caused by common viral infections and resolve on their own within a few days. Your main jobs are keeping your baby comfortable, watching for warning signs, and deciding whether medication is needed.
How to Take an Accurate Temperature
For babies under 3 years old, a rectal thermometer gives the most accurate reading. Ear thermometers become reliable at 6 months of age, so yours is just reaching the point where that’s a reasonable option. Forehead (temporal) thermometers work for babies 3 months and older. Armpit readings are the least reliable and are best used as a quick first check rather than a final answer.
The numbers that count as a fever depend on where you measure. A rectal, ear, or forehead reading of 100.4°F (38°C) or higher is a fever. An armpit temperature of 99°F (37.2°C) or higher is a fever. If you get a concerning armpit reading, follow up with a rectal measurement to confirm.
What’s Likely Causing the Fever
Viral infections are by far the most common cause of fever in babies. These include colds, flu, and other respiratory viruses. Bacterial infections like ear infections, urinary tract infections, and throat infections can also trigger fevers, though they’re less frequent. If your baby recently received vaccinations, a mild fever in the day or two afterward is normal and usually short-lived.
The fever itself isn’t the illness. It’s your baby’s immune system fighting off whatever bug is present. A higher number doesn’t automatically mean a more serious infection. How your baby is acting matters more than the exact temperature on the thermometer.
Keeping Your Baby Comfortable at Home
Hydration is the top priority. Offer breast milk or formula frequently. Do not give fruit juice. If your baby is vomiting, a pediatric electrolyte solution like Pedialyte can help replace lost fluids. Signs of dehydration to watch for include fewer wet diapers than usual, no tears when crying, and a dry mouth.
Dress your baby in one layer of lightweight clothing. It’s tempting to pile on blankets when they have the chills, but bundling can trap heat and push the fever higher. One light blanket for sleep is enough.
A lukewarm sponge bath can help bring the temperature down, but it works best when combined with fever-reducing medication. On its own, the cooling effect tends to be temporary and the fever bounces back. Never use cold water, ice, or alcohol rubs. These cause shivering, which actually raises the body’s core temperature and makes things worse.
When and How to Use Fever Medication
Acetaminophen (Tylenol) is safe for babies 3 months and older. You can give it every 4 to 6 hours as needed, with a maximum of 5 doses in 24 hours. The infant suspension comes in a concentration of 160 mg per 5 mL. Dosing is based on your baby’s weight, not age. A baby weighing 12 to 17 pounds typically gets 2.5 mL, while one weighing 18 to 23 pounds gets 3.75 mL. Check your product’s label to confirm the concentration matches.
Ibuprofen (Advil, Motrin) is an option now that your baby is 6 months old, though many pediatricians still prefer you check with them before starting it at this age. It’s given every 6 to 8 hours, with a maximum of 4 doses per day. Dosing is also weight-based. If your baby is under 6 months, ibuprofen is not safe to use without a doctor’s specific instruction.
You don’t need to medicate every fever. If your baby is eating, sleeping, and playing reasonably well, the fever may not need treatment at all. Medication is most useful when the fever is making your baby noticeably uncomfortable or fussy, or when it’s interfering with sleep or feeding.
Warning Signs That Need Immediate Attention
Most fevers in a 6-month-old are manageable at home, but certain signs mean you should get medical care right away:
- Difficulty breathing, including fast or labored breaths
- Unusual drowsiness or unresponsiveness, where your baby seems hard to wake or isn’t making eye contact
- Skin or lips that look blue, purple, or gray
- Persistent vomiting that prevents your baby from keeping fluids down
- A seizure of any kind
- Pain or fussiness that keeps getting worse or doesn’t improve with comfort measures and medication
- A rash that doesn’t fade when you press on it, which can signal a serious infection
Call your pediatrician if the fever lasts more than 2 to 3 days, if the temperature climbs above 102°F and doesn’t respond to medication, or if your baby seems to be getting worse rather than better over time. Trust your instincts. You know your baby’s normal behavior, and a change in how alert or interactive they are is worth a phone call even if the temperature isn’t dramatically high.
What to Know About Febrile Seizures
Febrile seizures happen in about 2 to 5 percent of children between 6 months and 5 years old, most commonly between 12 and 18 months. They’re triggered by the rapid rise in temperature rather than by how high the fever gets. While terrifying to witness, simple febrile seizures (lasting under 15 minutes, with no focal symptoms) do not cause brain damage or increase the risk of epilepsy.
If your baby has a seizure, place them on a firm, flat surface on their side. Don’t put anything in their mouth or try to restrain their movements. Time the seizure. Most stop on their own within a few minutes. If it lasts longer than 5 minutes, call emergency services. Any first-time seizure should be evaluated by a doctor, even if it stops quickly, to rule out other causes.