In short
Fever is the body's normal way of fighting infection, and in most children how they behave matters more than the number on the thermometer — except in babies under three months, where a fever of 100.4°F (38°C) or higher means calling a doctor right away.
Emergency if: Fever with a stiff neck, a rash that does not fade under a glass, a fit, confusion, being hard to wake, struggling to breathe or blue lips or skin: call emergency services now. A baby under 3 months at 38°C or higher: go to an emergency department now, unless a doctor can see your baby within 2 hours. A baby of 3 to 6 months at 39°C or higher: go to an emergency department now.
On your report
CRP, WBC / Total Leukocyte Count
On this page
01
Fever Is a Defense, Not a Disease
A fever is the immune system raising the body's temperature to make it harder for viruses and bacteria to multiply. It is a sign the body is actively responding to something, not an illness in its own right. Treating the underlying cause, and keeping a child comfortable, matters more than chasing a specific number down.
How a child is acting, alertness, appetite, whether they can be comforted, usually says more about severity than the exact temperature reading. A child with a high fever who is playful between spikes is often less concerning than one with a modest fever who is limp, unresponsive, or inconsolable.
02
Why Age Changes Everything
In babies under three months old, any fever of 100.4°F (38°C) or higher needs medical advice right away, no exceptions — call the doctor immediately, or go to an emergency department if you cannot reach one. Very young infants' immune systems cannot reliably fight off serious infections on their own, and the outward signs of a dangerous illness can look identical to a mild one at this age.
For older infants and children, the approach shifts toward watching behavior over hours, not minutes. Doctors may sometimes check blood tests, such as a white blood cell count or an inflammation marker, when a fever's source isn't obvious and they need more information to judge how the body is responding.
03
Febrile Seizures: Frightening but Usually Harmless
A febrile seizure, jerking movements, eyes rolling back, brief unresponsiveness, can happen in some children as a fever rises quickly, most often between six months and five years of age. It is deeply frightening to witness but typically lasts only a minute or two and stops on its own.
Febrile seizures are terrifying to watch and usually harmless — but the response depends on the situation. A first-ever seizure, any seizure in a baby under about six months, a seizure lasting more than five minutes, repeat seizures in the same illness, or a child who does not return to normal alertness afterward all mean calling emergency services now. During a seizure: place the child on their side on a safe surface, put nothing in the mouth, do not restrain them, and time it.
04
Comfort Measures That Help
Light clothing, a comfortably cool room, and steady fluids help a feverish child feel better without needing to force the number down. Overbundling a child "to sweat it out" doesn't speed recovery and can make a child more uncomfortable, especially in infants who can't easily regulate their own temperature.
Fever-reducing medicine, when a pediatrician has approved it for a child's age and weight, is for comfort, not obligation. A child who is drinking, resting, and interactive doesn't need medicine just because a number looks high; a miserable child may benefit from it even at a lower reading. One absolute rule: never give aspirin, or any aspirin-containing product, to a child or teenager with a fever or viral illness — it is linked to Reye syndrome, a rare but serious condition.
05
When to Call vs When to Go to the Emergency Department
Call the pediatrician right away, not later in the day, for a fever of 100.4°F (38°C) or higher in a baby under three months, or a fever with an unexplained rash. Call the same day for a fever lasting more than three to five days, a fever with ear pain or persistent vomiting, or any fever that returns after seeming to resolve. Trust your instinct if something feels off even without a textbook symptom.
Call emergency services now or go to an emergency department now for a first-ever seizure or one lasting more than five minutes, trouble breathing, blue or grey lips, a rash that does not fade when a glass is pressed against it, a stiff neck, a child who is hard to wake or unresponsive, no urine for 12 hours, or a temperature of 39°C or more in a baby aged 3 to 6 months. These signs mean the situation needs care now.
When to act
Emergency — act now
Fever with a stiff neck, a rash that does not fade under a glass, a fit, confusion, being hard to wake, struggling to breathe or blue lips or skin: call emergency services now. A baby under 3 months at 38°C or higher: go to an emergency department now, unless a doctor can see your baby within 2 hours. A baby of 3 to 6 months at 39°C or higher: go to an emergency department now.
Same-day — call promptly
Fever lasting 5 days or more, fever with a new rash, ear pain or repeated vomiting, fever that returns after settling, or fewer wet nappies: see your child's doctor today.
Routine — see a doctor
A child over 6 months with a fever who is drinking, alert and playful between spikes: comfort care at home and keep watching.
Values mentioned in this story
Each one opens a visual guide with its normal range and what moves it — upload a report and we place your own numbers on the same scale.
Sources
- Fevermedlineplus.gov
- When to get urgent medical help for babies and children under 5 — NHSnhs.uk
- Fever in under 5s (NG143) — NICEnice.org.uk
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