Why Do Fevers Get Worse at Night? A Pediatrician Explains

Why Does My Child's Fever Seem Higher at Night?

This is one of those patterns many parents notice during an illness.

Your child may seem fairly comfortable in the morning with a temperature around 100°F or 101°F.

By evening, the thermometer may read 102°F or 103°F.

That can make it seem as though the illness has suddenly taken a turn for the worse.

Often, however, part of what you are seeing is the body's normal daily temperature rhythm.

Does Body Temperature Normally Change During the Day?

Yes.

Normal body temperature is not exactly the same every hour of the day.

The American Academy of Pediatrics notes that body temperature is generally lowest between midnight and early morning and highest between late afternoon and early evening.

This happens even when a person is not sick.

When a child already has a fever-producing illness, that normal rhythm may contribute to a higher temperature later in the day.

Parents sometimes wonder whether exhaustion itself can also raise a child's temperature. For more detail, see Can a Child Have a Fever From Being Overtired?

Can Fever Medicine Wearing Off Make the Fever Look Worse at Night?

Yes.

Suppose your child receives fever medicine in the afternoon and becomes more comfortable.

Several hours later, the medication effect begins to wear off at the same time that normal body temperature is tending to rise.

The result may be a noticeable evening increase in temperature.

That does not mean the medicine failed.

Fever medicine temporarily reduces fever and discomfort. It does not eliminate the infection causing the fever.

Does a Nighttime Fever Mean My Child Is Getting Sicker?

Not necessarily.

The time of day is much less important than your child's overall condition.

Ask:

• Is my child breathing comfortably?
• Are they drinking?
• Are they urinating?
• Are they alert when awake?
• Do they recognize and respond normally to me?
• Do they become somewhat more comfortable when the fever decreases?
• Are new or worsening symptoms appearing?

Those observations tell you much more about how sick a child may be than whether the temperature rose at 8 p.m. instead of 10 a.m.

Should I Wake My Child Because the Fever Might Rise Overnight?

A comfortably sleeping older infant or child generally does not need to be repeatedly awakened simply so you can check the thermometer.

Sleep is helpful during illness.

However, circumstances matter. A very young infant, a child who is seriously ill, or a child whose healthcare professional has given specific monitoring instructions may require a different approach.

If you are concerned about your child's breathing, responsiveness or overall condition, check them rather than relying on the fact that they are asleep.

Should I Wake My Child to Give Fever Medicine?

Fever medicine is generally used for comfort.

If an older child is sleeping comfortably, there usually is not a need to wake them solely to normalize the temperature unless your healthcare professional has specifically instructed you otherwise.

Fever medication should not be used on a rigid schedule simply because the thermometer shows a fever.

What If My Child Wakes Up Hot and Uncomfortable?

First look at your child.

Offer fluids if they are awake enough to drink.

Keep clothing and blankets comfortable rather than excessively heavy.

If your child is uncomfortable and fever medicine is appropriate, use the correct weight-based dose and dosing interval.

Should I Keep Checking the Temperature All Night?

Usually not.

Repeated thermometer checks can keep both you and your child awake without providing much useful information.

If your child is resting comfortably, breathing normally and does not have other concerning symptoms, you generally can allow them to sleep.

Check your child if something seems wrong or if your healthcare professional has advised more frequent monitoring.

Is a Fever More Dangerous Because It Happens at Night?

No.

A fever does not become inherently more dangerous simply because it occurs at night.

The same warning signs apply whether it is 2 p.m. or 2 a.m.

What can make nighttime illness feel more frightening is that the pediatrician's office may be closed, parents are tired, and symptoms can feel more dramatic in a quiet house.

But the medical assessment still depends on your child's age, symptoms and overall condition.

What If the Fever Is 104°F at Night?

A temperature of 104°F is high and deserves attention.

The American Academy of Pediatrics recommends contacting your child's doctor when temperatures repeatedly rise above 104°F (40°C).

But even then, look at the whole child.

A child who is alert, drinking and breathing comfortably presents differently from a child who is difficult to wake, dehydrated, confused or struggling to breathe.

How Long Should a Fever Last?

Many common viral illnesses produce fever for a few days.

The American Academy of Pediatrics recommends contacting your child's doctor when fever lasts:

• more than 24 hours in a child younger than 2 years, or
• more than 3 days (72 hours) in a child age 2 or older.

Do not wait for those time limits if your child appears seriously ill or has concerning symptoms.

What If My Baby Is Younger Than 3 Months?

When Should I Call My Pediatrician?

When Should I Seek Emergency Care?

The Bottom Line

It is common for parents to notice that a child's fever seems higher in the evening.

Normal body temperature itself tends to rise later in the day, and fever medication given earlier may also be wearing off.

A nighttime rise in temperature does not automatically mean your child's illness is becoming more serious.

Look at your child's breathing, hydration, alertness, behavior and other symptoms rather than focusing only on the time of day or thermometer reading.

And if your baby is younger than 3 months and has a temperature of 100.4°F (38°C) or higher, seek prompt medical guidance regardless of whether it happens during office hours or in the middle of the night.