Baby Fever: When to Call the Doctor
My baby feels hot — do I need to call the doctor right now?
Fever is your baby's immune system doing its job. What matters is your baby's age and how they act. This guide gives you the temperature thresholds by age and the signs that mean call now.
Reviewed against current AAP and CDC guidance
What counts as a fever
A fever is a rectal, oral, ear, or forehead temperature of 100.4°F (38°C) or higher. Fever is not an illness. It is a normal immune response — the body raises its temperature to help fight infection, which stimulates immune defenses such as white blood cells that attack invading viruses and bacteria. The number alone does not tell you how sick your baby is. In a baby 3 months or younger, any fever is treated as urgent regardless of how well they seem. In an older baby, how your baby looks and acts matters more than the exact reading.
Call 911 or go to the ER now
- Severe trouble breathing — struggling for each breath, or can barely cry
- Blue or bluish lips, face, or skin
- Will not wake up, or is hard to wake and not alert when awake
- A seizure that lasts more than 5 minutes, or trouble breathing or turning blue during a seizure
- Stiff neck — cannot move the neck normally
- Purple or blood-colored spots or dots on the skin that do not fade when pressed
- A bulging or swollen soft spot in a baby under 1 year
- Acts confused or cannot be roused to normal alertness
- You think your baby has a life-threatening emergency
Call your pediatrician now
- Your baby is 3 months or younger with a rectal temperature of 100.4°F (38°C) or higher — call immediately, even if your baby seems fine
- Any age, with a fever that repeatedly rises above 104°F (40°C)
- Looks severely ill, is unusually drowsy or lethargic, or is very fussy and hard to console
- Stiff neck, severe headache, severe sore throat, or severe ear pain
- Trouble breathing
- An unexplained rash, or repeated vomiting or diarrhea
- Signs of dehydration: no wet diaper in more than 8 hours, dark urine, a very dry mouth, or no tears when crying
- Fever lasts more than 24 hours in a baby under 2 years
- Fever lasts more than 3 days (72 hours) in a child 2 years or older
- Still acts sick after the fever comes down, or symptoms are getting worse
What to do by age
- Any rectal temperature of 100.4°F (38°C) or higher means call your pediatrician immediately or go to the ER.
- Do this even if your baby is feeding, sleeping, and acting normally. A fever at this age can be the only sign of a serious infection.
- Do not give fever medicine before talking to a doctor.
- Use a rectal thermometer for the reading — it is the most accurate at this age.
Calling for any fever this young is the correct response, not an overreaction.
- Call your pediatrician if the temperature reaches 101°F (38.3°C) or higher.
- Call sooner, at any temperature, if your baby seems unusually drowsy, very fussy, or is feeding poorly.
- Watch for the red flags above between calls.
At this age, how your baby acts starts to matter alongside the number.
- Call your pediatrician if the temperature reaches 103°F (39.4°C) or higher.
- Call if a lower fever lasts more than 24 hours in a baby under 2 years, even without other symptoms.
- Offer fluids often. Acetaminophen or ibuprofen can ease discomfort — for a baby under 2 years, ask your pediatrician or pharmacist for the correct dose first.
A comfortable, drinking, interactive baby with a fever is usually fighting a routine infection.
- Call your pediatrician if the fever repeatedly rises above 104°F (40°C), or lasts more than 3 days (72 hours).
- Call any time your child looks severely ill, is hard to wake, or has the red flags above.
- Treating the fever is about comfort, not the number — a child who is playing and drinking may not need medicine at all.
Many fevers at this age can be managed at home with fluids and rest.
How to take your baby's temperature
| Age | Best method | Notes |
|---|---|---|
| Under 3 months | Rectal | Gives the best reading and is the one to report to the doctor. Avoid ear thermometers — the ear canal is too small. |
| 3 months–4 years | Rectal or forehead | Rectal gives the most accurate reading. Forehead (temporal artery) works at any age and is an acceptable option. |
| 6 months and older | Rectal, forehead, or ear | Ear (tympanic) can be used from 6 months and up, once the ear canal is large enough. |
| 4 years and older | Oral | Once your child can hold the thermometer under the tongue with the mouth closed. |
Fever medicine: the basics
- Acetaminophen or ibuprofen can lower a fever and ease aches. The goal is comfort, not a normal number on the thermometer.
- Ibuprofen is for babies 6 months and older. For a baby under 3 months, call your doctor before giving any fever medicine.
- If your child is under 2 years, ask your pediatrician or pharmacist for the correct dose. For older children, follow the dose on the label.
- Never give aspirin to a child for a fever.
- Skip alcohol baths, ice packs, and cold sponging — these are no longer recommended and can harm your child.
- Keep offering fluids to prevent dehydration.
About febrile seizures
Febrile seizures can happen in children between 6 months and 5 years of age, most often around 12 to 18 months, usually in the first few hours of a fever. They are frightening to watch but most are short and do not cause brain damage or lasting harm. Most last less than one or two minutes. Place your child on the floor or bed away from hard objects, turn their head to the side so saliva can drain, and do not put anything in the mouth. Call 911 if the seizure lasts more than 5 minutes, or if your child has trouble breathing or turns blue. Call your pediatrician right away after any febrile seizure — a first seizure needs an exam to find the cause.
Quick answers
- My baby is under 3 months with a fever. What temperature means call the doctor?
- A rectal temperature of 100.4°F (38°C) or higher in a baby 3 months or younger means call your pediatrician immediately or go to the ER. Do this even if your baby is feeding and acting normally. At this age, fever can be the only sign of a serious infection, so it is always treated as urgent.
- Is a fever dangerous for my baby?
- Fever itself is usually not dangerous. It is a normal immune response that helps the body fight infection. What matters is your baby's age and how they act. For babies under 3 months, any fever of 100.4°F (38°C) or higher needs an immediate call. For older babies, watch for red flags like trouble breathing, a stiff neck, a non-fading rash, being very hard to wake, or signs of dehydration, and call if the fever repeatedly tops 104°F (40°C).
- What's the best way to take my baby's temperature?
- For babies under 3 months, a rectal temperature gives the best reading and is the one to report to the doctor. Avoid ear thermometers in babies under 6 months because the ear canal is too small. Forehead (temporal artery) thermometers can be used at any age, and ear thermometers can be used from 6 months. A fever is 100.4°F (38°C) or higher by rectal, oral, ear, or forehead reading.
- How long can a fever last before I call the doctor?
- Call your pediatrician if a fever lasts more than 24 hours in a baby under 2 years, or more than 3 days (72 hours) in a child 2 years or older. Call sooner at any age if your child looks severely ill, is hard to wake, has trouble breathing, or shows signs of dehydration such as no wet diaper in over 8 hours or no tears when crying.
- Can I give my baby medicine to bring the fever down?
- Acetaminophen or ibuprofen can lower a fever and ease discomfort, but the goal is comfort, not a perfect number. Ibuprofen is for babies 6 months and older. If your child is under 2 years, ask your pediatrician or pharmacist for the correct dose first. Never give aspirin. For a baby under 3 months, call your doctor before giving any fever medicine.
Sources & further reading
Keep temps, symptoms, and meds in one place.
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App Store Google Play Open Web AppThis guide reflects current AAP and CDC guidance and is for educational purposes only. It does not constitute medical advice. ParentFlow is a wellness companion — not a substitute for your pediatrician. For any medical concern, contact your healthcare provider.