Free newborn guide

Baby fever: the number depends on where you measured.

Every page you will read about baby fever gives you one number, as if it were the same number everywhere. It is not. Rectal, ear and forehead have one published cutoff; mouth has two published cutoffs that disagree; armpit has the lowest one and the least reliable device. Add the age rule and the duration rule and you have a threshold that moves. This page reports every published number with its source, names the two published boundaries for the “under 3 months” rule instead of quietly picking one, and gives you a checker that says which published rule your reading meets — and, always, that a reading below the cutoff does not rule fever out.

What to do right now Check my reading

FreeNo accountNothing uploadedSourced guidance

Read this first

1. Symptoms outrank numbers

The published reasons to call are mostly things you can see — not alert when the fever drops, no tears, no wet diapers for 8 hours, hard to wake. None of them depends on a temperature.

2. Any fever under 3 months is a call

AAP says immediately, “even if your baby shows no other signs or symptoms of being ill”. And do not give fever medicine before the baby is seen.

3. “Under 3 months” has two published boundaries

12 weeks (84 days) and 3 calendar months. Those dates differ, and a baby can sit between them. Both are shown below.

4. A low reading is not clearance

The 2020 meta-analysis of 46 studies says plainly “finding a temperature below 38 °C does not rule out fever”. That is the one sentence this page will not let you miss.

Before anything else

What to do right now, not after you finish reading.

These are the published emergency and call-now lists, plus the medicine rules that apply before a young baby has been seen. They are the first section on this page on purpose: a page about fever thresholds is dangerous if it puts a number above a symptom.

Call 911 right nowA baby who is crying and cannot be calmed down, cannot be awakened easily or at all, seems confused, cannot walk, has difficulty breathing even after their nose is cleared, has blue lips, tongue or nails, has a very bad headache, has a stiff neck, refuses to move an arm or leg, has a seizure, or has a new rash or bruises appear. MedlinePlus lists every one of these under Call 911.

Any fever in a baby under 3 monthsAAP: call your pediatrician immediately for a rectal reading of 100.4 °F (38 °C) or higher, “even if your baby shows no other signs or symptoms of being ill”. HealthyChildren’s symptom checker puts “Fever in baby less than 12 weeks old” under Call Doctor or Seek Care Now. The boundary is published two ways and this page names both below rather than picking one silently.

No fever medicine before a young baby is seenAAP symptom checker: “do NOT give your baby any fever medicine before being seen.” Mayo: “for children younger than age 3 months, don’t give acetaminophen until your baby has been seen by your healthcare team.” MedlinePlus: “In children under 3 months of age, contact your child’s provider first before giving them medicines.”

Never give aspirinMedlinePlus: “Do not give aspirin to children unless your child’s provider tells you it is OK.” Mayo: “Don’t use aspirin to treat a fever in anyone age 18 years or younger.”

No ibuprofen under 6 monthsMedlinePlus: “Do not use ibuprofen in children younger than 6 months old.” Mayo: “If you want to give your child medicine to treat a fever, stick to acetaminophen (Tylenol, others) until age 6 months.”

Anything that looks wrong is a call, whatever the number saysMedlinePlus lists these as reasons to call or go to the emergency room on their own: “Your child does not act alert or more comfortable when their fever goes down”, “Fever symptoms come back after they had gone away”, “Your child does not make tears when crying”, “Your child does not have wet diapers or has not urinated in the past 8 hours.” None of those depends on a temperature.

If you think it is heatstroke, not feverAAP: “If you think your child has heatstroke, call 911 or go to the emergency department right away.” Heatstroke is not caused by infection, and body temperature can rise “above 105 degrees Fahrenheit [40.5 degrees Celsius]”. Also, from the same source: “Never leave your baby alone in closed car, even for a few minutes.”

Emergency and crisis lines

Poison Control1-800-222-1222 — for medicine dosing errors and suspected overdose 988 LifelineU.S. crisis support, for you as well as for them National Maternal Mental Health Hotline1-833-TLC-MAMA (1-833-852-6262) — free, confidential, 24/7, English and Spanish, for new parents. HRSA’s own words: “New parents: you’re not alone.”

Call emergency services for a baby who is unresponsive, struggling to breathe, turning blue, or having a seizure. That is the site-wide rule and it applies here.

If it might be heatstroke

AAP: “Fever should not be confused with heat-related illness, or heatstroke. This is not caused by infection.” Body temperature with heatstroke can rise “above 105 degrees Fahrenheit [40.5 degrees Celsius]”. The same source: “If you think your child has heatstroke, call 911 or go to the emergency department right away.”

The part most pages leave out

Three published answers, not one.

The cutoffs are published per measurement site, and two authorities publish different numbers for the same site. Rather than pick the tidier one, this page shows you the table the sources actually draw.

Where you measured	The published cutoff for a fever
Rectal (bottom)	100.4 °F Mayo Clinic / 100.4 °F AAP HealthyChildren
Ear (tympanic)	100.4 °F Mayo Clinic
Forehead (temporal artery)	100.4 °F Mayo Clinic
Mouth (oral)	100.0 °F Mayo Clinic / 100.4 °F AAP HealthyChildren
Armpit (axillary)	99.0 °F Mayo Clinic / 99.0 °F AAP HealthyChildren symptom checker

“Under 3 months” is published two ways. AAP, MedlinePlus and Mayo all write it as 3 months of age or younger. HealthyChildren’s symptom checker writes the same rule as less than 12 weeks old. 12 weeks is exactly 84 days; 3 calendar months lands between 84 and 92 days depending on the birth date. Between those two dates, a baby is inside one published rule and outside the other — and the difference matters, because the under-3-months rule is the one with no symptom requirement at all. The checker below gives you both of your baby’s dates and tells you which rules each one triggers.

The most common shortcut on this subject is “add a degree to an armpit reading”. The literature argues about it. PubMed 8542011 endorsed it for over-1-month-olds; the BMJ systematic review of 3,201 participants concluded the variation is too wide for it to hold; and a 2020 meta-analysis of 46 studies measured axillary digital thermometry lower by 0.67 °C than rectal with a reproducibility of 1.2 °C. Three positions. This page does not hand you the conversion.

Published age boundary	What the source says
12 weeks (84 days)	AAP HealthyChildren symptom checker: “Fever in baby less than 12 weeks old.”
3 calendar months	AAP / MedlinePlus / Mayo: “3 months of age or younger”, “younger than age 3 months”.

Every published rule that applies, with its source

Which published rule does your reading meet?

Enter the date of birth, choose how you took the temperature, and enter the reading. The checker reports which published cutoffs apply to that measurement site, which published call thresholds apply to that age — each one named with its own source — and the envelope across them. It also tells you when the device you used is one the sources say is not accurate at that age. It never tells you your baby is fine.

1. Date of birth

2. How was it measured?

3. The reading (°F)

4. How long has the fever lasted? (optional)

5. Anything here? (published reasons to call, independent of any number) Not acting alert, or not more comfortable, when the fever goes down Fever came back after it had gone away Not making tears when crying No wet diapers, or has not urinated in the past 8 hours Looks unusually irritable, lethargic or uncomfortable Difficulty breathing, even after the nose is cleared A seizure Something you cannot explain, that feels wrong

The thresholds, by age and source

Every published call threshold in one table.

This is the whole reason the page exists. The same age band has more than one published threshold, and they are not close in every case: for a 4-month-old the published numbers are 101 °F and 102.2 °F. Notice too which rows are stated for a rectal reading specifically — the under-3-months rules are — because that is where a peripheral reading stops being able to answer the question.

Published rule	Threshold	Stated for	Source
Any fever under 12 weeks old	—	any site	AAP symptom checker
3 months or younger, rectal 100.4 or higher	100.4 °F	rectal reading	AAP HealthyChildren
Younger than 3 months, rectal 100.4 or higher	100.4 °F	rectal reading	MedlinePlus
Younger than 3 months, rectal 100.4 or higher	100.4 °F	rectal reading	Mayo Clinic
3 to 6 months, fever of 101 or greater	101.0 °F	any site	AAP HealthyChildren
3 to 6 months: up to 101 with symptoms, or above 101	101.0 °F	any site	Mayo Clinic
3 to 12 months, fever of 102.2 or higher	102.2 °F	any site	MedlinePlus
Older than 6 months, temperature of 103 or higher	103.0 °F	any site	AAP HealthyChildren
6 to 24 months: above 101 lasting longer than one day	101.0 °F	any site	Mayo Clinic
Under 2 years, a fever lasting longer than 48 hours	—	any site	MedlinePlus
6 to 12 months: fever longer than 48 hours or more than 3 days	—	any site	AAP symptom checker
A fever over 105 F	105.0 °F	any site	MedlinePlus
A fever higher than 104 F	104.0 °F	any site	AAP symptom checker

Published figures, verbatim

The numbers behind every sentence above.

No figure on this page is invented or converted. Each one is a restatement of the source beside it, and the checker computes only from these numbers.

What the question is	What the published guidance says	Source
What counts as a fever, by site	Mayo Clinic: “A rectal, ear or temporal artery temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher. An oral temperature of 100 degrees Fahrenheit (37.8 degrees Celsius) or higher. An armpit temperature of 99 degrees Fahrenheit (37.2 degrees Celsius) or higher.” AAP HealthyChildren: “a rectal temperature reading of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher is considered a fever”, and for “oral (mouth), tympanic (ear) or temporal artery” readings you “should still generally use 100.4 degrees Fahrenheit or more as the cutoff for a true fever”; axillary “measurements may have a lower cutoff”. HealthyChildren’s symptom checker: “Under the arm (armpit) temperature: 99 °F (37.2 °C) or higher”.	Mayo Clinic; AAP HealthyChildren; AAP symptom checker
The two published boundaries for “under 3 months”	AAP: “If your baby is 3 months of age or younger and has a rectal temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, call your pediatrician immediately. This is very important, even if your baby shows no other signs or symptoms of being ill.” HealthyChildren’s symptom checker uses a different boundary for the same rule: “Fever in baby less than 12 weeks old.” 12 weeks is 84 days; 3 calendar months is 84 to 92 days depending on the birth date. A baby between those two dates is inside one published rule and outside the other.	AAP HealthyChildren; AAP symptom checker
3 months or younger: the call rule	AAP: call your pediatrician “immediately” for a rectal reading of 100.4 °F or higher, “even if your baby shows no other signs or symptoms of being ill”. MedlinePlus: “Is younger than age 3 months and has a rectal temperature of 100.4°F (38°C) or higher.” Mayo: “Your child is younger than age 3 months and has a rectal temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher.” All three agree, and all three state it for a RECTAL reading.	AAP HealthyChildren; MedlinePlus; Mayo Clinic
Why the under-3-months rule is absolute	AAP clinical practice guideline: “About 14 out of every 1,000 healthy infants born full term develop a fever during the ages 8 days to 60 days old.” “More than 10% of febrile infants are diagnosed with a urinary tract infection. The likelihood of a more invasive bacterial infection is much lower, with fewer than .05% of infants developing meningitis, the most serious infection.” HealthyChildren’s symptom checker: “Fever that occurs during the first 3 months of life can be serious. All of these babies need to be seen as soon as possible.”	AAP infant fever guideline; AAP symptom checker
3 to 6 months: the call rule	AAP: “you also may need to notify the doctor if your child is between 3 and 6 months and has a fever of 101 degrees Fahrenheit (38.3 degrees Celsius) or greater”. Mayo: “Your child is age 3 to 6 months and has a temperature up to 101 degrees Fahrenheit (38.3 degrees Celsius) and seems unusually irritable, lethargic or uncomfortable, or has a temperature higher than this number.” MedlinePlus covers the same ages with a higher number: “Is 3 to 12 months old and has a fever of 102.2°F (39°C) or higher.”	AAP HealthyChildren; Mayo Clinic; MedlinePlus
6 months and older: the call rule	AAP: “is older than 6 months and has a temperature of 103 degrees Fahrenheit (39.4 degrees Celsius) or higher” — “Such a high temperature may point to a significant infection or dehydration, which may need treatment.” Mayo: “Your child is age 6 to 24 months and has a temperature higher than 101 degrees Fahrenheit (38.3 degrees Celsius) that lasts longer than one day but shows no other signs.” Note that these two are conditioned differently: AAP’s is a number, Mayo’s is a number plus a duration.	AAP HealthyChildren; Mayo Clinic
How long the fever has lasted	MedlinePlus: “Is under age 2 and has a fever that lasts longer than 48 hours.” HealthyChildren’s symptom checker, under “Contact Doctor Within 24 Hours”: “Age 6-12 months old with fever that lasts more than 48 hours”, and “Fever lasts more than 3 days”.	MedlinePlus; AAP symptom checker
Very high numbers	MedlinePlus: “Has a fever over 105°F (40.5°C), unless the fever comes down readily with treatment and the child is comfortable.” HealthyChildren’s symptom checker, under “Call Doctor or Seek Care Now”: “Fever higher than 104 °F (40 °C)”.	MedlinePlus; AAP symptom checker
Symptoms outrank numbers	MedlinePlus lists these under “When to Call the Doctor” as conditions in their own right, independent of any temperature: “Your child does not act alert or more comfortable when their fever goes down”; “Fever symptoms come back after they had gone away”; “Your child does not make tears when crying”; “Your child does not have wet diapers or has not urinated in the past 8 hours.” And under Call 911: “Is crying and cannot be calmed down”, “Cannot be awakened easily or at all”, “Seems confused”, “Has difficulty breathing, even after their nose is cleared”, “Has blue lips, tongue, or nails”, “Has a very bad headache”, “Has a stiff neck”, “Refuses to move an arm or leg”, “Has a seizure”, “Has a new rash or bruises appear”.	MedlinePlus
A below-cutoff reading does not rule fever out	2020 systematic review and network meta-analysis, 46 studies, more than 12,000 patients: “Several peripheral thermometers proved specific, but not sensitive for diagnosing fever with rectal thermometry as a reference standard, meaning that finding a temperature below 38 °C does not rule out fever.” The pooled sensitivity at a 38 °C cut-off was 0.76 (95% CI 0.65-0.84) for temporal infrared and 0.77 (0.60-0.88) for tympanic infrared thermometry.	Internal and Emergency Medicine, 2020 (network meta-analysis)
How far apart the sites actually measure	2020 network meta-analysis, against rectal mercury-in-glass as the reference: “axillary digital thermometry was significantly lower by −0.67 °C (−0.98, −0.37)”, and the “median coefficient of reproducibility” ranged “between 0.53 °C [0.95 °F] for infrared temporal and 1.2 °C [2.16 °F] for axillary digital thermometry”. BMJ systematic review of axillary vs rectal: the pooled “mean temperature difference (rectal minus axillary temperature) for electronic thermometers was 0.85°C (−0.19°C to 1.90°C)”.	Internal and Emergency Medicine, 2020; BMJ, PMC27359
The “add a degree” rule is contested	PubMed 8542011 (1995): “the axillary temperature plus 1 degree C is a good guide to the rectal temperature in patients older than 1 month.” The BMJ systematic review of 20 studies and 3,201 participants reaches the opposite conclusion: “It is believed that rectal temperature can be estimated by adding 1 C to the temperature measured at the axilla. The wide range in the mean differences we have detected suggests that this is not the case.” Three published positions on one popular rule.	PubMed 8542011; BMJ PMC27359; Internal and Emergency Medicine 2020
Which device is allowed at which age	Mayo: “Birth to 3 months. Use a regular digital thermometer to take a rectal temperature.” “Wait until your baby is at least 6 months old to use a digital ear thermometer.” AAP: “Avoid using an ear thermometer for babies under 6 months old”; “Using temperature sensitive tape or ‘fever strips’ also is not reliable.” Mayo: “Digital pacifier thermometers and fever strips are not recommended.”	Mayo Clinic; AAP HealthyChildren
Fever medicine, by age	AAP symptom checker: “do NOT give your baby any fever medicine before being seen” for a fever in a baby less than 12 weeks old. MedlinePlus: “In children under 3 months of age, contact your child’s provider first before giving them medicines”; “Do not use ibuprofen in children younger than 6 months old”; “Do not give aspirin to children unless your child’s provider tells you it is OK.” Mayo: “for children younger than age 3 months, don’t give acetaminophen until your baby has been seen by your healthcare team”; “Don’t use aspirin to treat a fever in anyone age 18 years or younger.”	AAP symptom checker; MedlinePlus; Mayo Clinic
Teething does not cause a true fever	AAP: “Teething, which often starts at about 6 months of age, can cause a slight rise in your baby’s body temperature within the normal range. However, research shows teething does not cause a true fever. If your child seems particularly miserable or has a fever higher than 100.3 degrees Fahrenheit (38 degrees Celsius), it’s probably not from teething; you should consult your pediatrician, as your baby may be sick.”	AAP HealthyChildren
Febrile seizures	AAP: “In children between 6 months old and 5 years of age, fever can trigger seizures.” “The entire febrile seizure typically last less than one minute—or even just a few seconds—though it can seem like forever to a frightened parent.” “if your baby has a febrile seizure, be sure to tell your pediatrician promptly. If your child is having trouble breathing or the febrile seizure does not stop within 15 minutes, call 911.”	AAP HealthyChildren
Heatstroke is not fever	AAP: “Fever should not be confused with heat-related illness, or heatstroke. This is not caused by infection.” “With heatstroke, body temperature can rise to dangerous levels (above 105 degrees Fahrenheit [40.5 degrees Celsius]).” “If you think your child has heatstroke, call 911 or go to the emergency department right away.” And: “Never leave your baby alone in closed car, even for a few minutes.”	AAP HealthyChildren
Report the reading AND how you took it	Mayo: “When reporting a temperature to your child’s care team, give the reading and explain how the temperature was taken.” That is why the log on this page has a column for the site and the device, not just the number.	Mayo Clinic

Febrile seizures

If the fever came with a seizure.

AAP: “In children between 6 months old and 5 years of age, fever can trigger seizures. These are called febrile seizures.” They “tend to run in families and usually happen during the first few hours of febrile illness”. During one, “a child may get an odd look on their face for a few moments, then stiffen or twitch and roll their eyes. They will be unresponsive for a short time.”

AAP: “The entire febrile seizure typically last less than one minute—or even just a few seconds—though it can seem like forever to a frightened parent.” The same source says they are “almost always” harmless and cause “no lasting damage to the brain or nervous system”. It also gives two instructions, and this page keeps them together: “if your baby has a febrile seizure, be sure to tell your pediatrician promptly”, and “If your child is having trouble breathing or the febrile seizure does not stop within 15 minutes, call 911.”

Two things in the same paragraph, not one without the other.

A source that says seizures are usually harmless is not a source that says to ignore one. Mayo: contact your child’s care team if “Your child with a fever has a febrile seizure for the first time.” MedlinePlus lists “Has a seizure” under Call 911. The 15-minute and breathing boundaries from AAP are in the card beside this.

Printable

A fever log the care team can actually use.

Mayo: “When reporting a temperature to your child’s care team, give the reading and explain how the temperature was taken.” So this log has a column for the site and device, not just the number — because 99.8 in an armpit and 99.8 in the rectum are not the same fact.

Fever log — bring this to the appointment

Record the method every time. The published guidance asks for it, and the number means different things by site.

Date / time	How measured (site & device)	Reading	Medicine given (what, how much, when)	Behavior, feeding, wet diapers	Question for the care team

Baby’s date of birth: ______________ · Care team / after-hours number: ____________________ · Weight, if known: __________

Questions dads actually ask

The honest answers.

What temperature counts as a fever?

It depends on where you measured, and two authorities publish different numbers for the same site. Mayo Clinic puts rectal, ear and temporal artery at “100.4 degrees Fahrenheit (38 degrees Celsius) or higher”, oral at “100 degrees Fahrenheit (37.8 degrees Celsius) or higher”, and armpit at “99 degrees Fahrenheit (37.2 degrees Celsius) or higher”. AAP says a rectal reading of 100.4 or higher is a fever, and that for oral, ear or temporal readings you “should still generally use 100.4 degrees Fahrenheit or more as the cutoff”. So for a mouth reading the published cutoffs are 100.0 and 100.4. This page shows both instead of picking one.

My baby is 12 weeks and 3 days old. Is he in the “under 3 months” group?

That is exactly the seam this page exists to name. The rule is published with two different boundaries. HealthyChildren’s symptom checker says “Fever in baby less than 12 weeks old” — 84 days. AAP, MedlinePlus and Mayo all say “3 months of age or younger” — a calendar boundary that falls between 84 and 92 days after birth, depending on the date. At 87 days old a baby is outside the 12-week rule and inside the 3-month rule. The page reports both boundaries with the dates for your baby and tells you which rules each one triggers, rather than resolving the difference by picking the answer that reads more tidily.

Why not just add a degree to an armpit reading?

Because the literature does not settle it. PubMed 8542011 (1995) concluded that “the axillary temperature plus 1 degree C is a good guide to the rectal temperature in patients older than 1 month”. The BMJ systematic review of 20 studies and 3,201 participants concluded the opposite: “It is believed that rectal temperature can be estimated by adding 1 C to the temperature measured at the axilla. The wide range in the mean differences we have detected suggests that this is not the case.” And a 2020 network meta-analysis of 46 studies measured axillary digital thermometry “significantly lower by −0.67 °C (−0.98, −0.37)” than rectal, with a reproducibility of 1.2 °C. Three published answers. This page reports the disagreement instead of handing you a conversion it cannot support.

A below-cutoff reading means my baby does not have a fever, right?

No, and this is the most important thing on the page. The 2020 systematic review and network meta-analysis, pooling 46 studies and more than 12,000 patients, states it directly: peripheral thermometers are “specific, but not sensitive for diagnosing fever with rectal thermometry as a reference standard, meaning that finding a temperature below 38 °C does not rule out fever.” Pooled sensitivity at a 38 °C cut-off was 0.76 for temporal and 0.77 for tympanic infrared. A low reading is a reason to measure again a different way, not a reason to stop.

Why is any fever under 3 months treated so differently?

Because the published guidance says so without qualification. AAP: “If your baby is 3 months of age or younger and has a rectal temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, call your pediatrician immediately. This is very important, even if your baby shows no other signs or symptoms of being ill.” The AAP clinical practice guideline gives the scale: “About 14 out of every 1,000 healthy infants born full term develop a fever during the ages 8 days to 60 days old”, and “More than 10% of febrile infants are diagnosed with a urinary tract infection.” Bacterial infection in this age group can progress quickly, so the rule is a number, not a judgement call.

Can I use an ear thermometer on a 3-month-old?

The sources say no. Mayo: “Wait until your baby is at least 6 months old to use a digital ear thermometer.” AAP: “Avoid using an ear thermometer for babies under 6 months old, since their ear canals are too small to allow an accurate reading.” HealthyChildren’s symptom checker: “ear temperatures are not accurate before 6 months of age.” Mayo’s age guidance for birth to 3 months is to “Use a regular digital thermometer to take a rectal temperature.” If you have already taken an ear reading on a young baby, the page will tell you the reading is not one you can act on in either direction.

Do I need to treat the fever itself?

The sources frame this mostly around comfort and age, not the number. Mayo: “If your child is older than 6 months and is drinking plenty of fluids, sleeping well and continuing to play, there’s usually no need to treat the fever.” MedlinePlus: “A fever does not need to come all the way down to normal. Most children will feel better when their temperature drops by even one degree.” MedlinePlus also warns on method: “Do not use cold baths, ice, or alcohol rubs. These often make the situation worse by causing shivering.” None of this page’s content tells you to give or withhold medicine for your baby; that is your care team’s call.

My baby had a seizure with the fever.

AAP: “In children between 6 months old and 5 years of age, fever can trigger seizures.” “The entire febrile seizure typically last less than one minute—or even just a few seconds—though it can seem like forever to a frightened parent.” The same source says febrile seizures are “almost always” harmless, AND gives the two things to do: “be sure to tell your pediatrician promptly”, and “If your child is having trouble breathing or the febrile seizure does not stop within 15 minutes, call 911.” Mayo adds: contact your care team if your child has “a febrile seizure for the first time”.

Does teething cause a fever?

AAP is explicit: “research shows teething does not cause a true fever.” Teething “can cause a slight rise in your baby’s body temperature within the normal range”, but “If your child seems particularly miserable or has a fever higher than 100.3 degrees Fahrenheit (38 degrees Celsius), it’s probably not from teething; you should consult your pediatrician, as your baby may be sick.” A baby with a fever and sore gums needs the fever explained, not attributed to the gums.

Sources

Where every figure on this page comes from.

Every number above is a restatement of one of these. If a source says something this page states, the words are quoted; if the sources disagree, both are shown.

AAP HealthyChildren — Fever and Your BabyThe cutoffs by site, the under-3-months rule, teething, febrile seizures, heatstroke AAP HealthyChildren — Fever symptom checker (0-12 months)The 12-week boundary, the 104 threshold, the ear and forehead-strip cautions, the “no fever medicine before being seen” rule MedlinePlus — When your baby or infant has a feverThe 3-12-month threshold, the 48-hour rule, the over-105 threshold, the Call 911 list, the medicine rules Mayo Clinic — Thermometer basics: taking your child’s temperatureThe cutoff by site including oral and armpit, the device age guidance, the measurement instructions AAP — Infant Fever clinical practice guideline“About 14 out of every 1,000 healthy infants born full term develop a fever during the ages 8 days to 60 days old” Internal and Emergency Medicine, 2020 — thermometer accuracy network meta-analysis“finding a temperature below 38 °C does not rule out fever”, the pooled sensitivities, the −0.67 °C axillary offset BMJ — Temperature measured at the axilla compared with rectum in childrenThe 0.85 °C pooled difference and the refusal of the “add 1 °C” rule PubMed 8542011 — Rectal, axillary, and forehead temperaturesThe opposing position on “axillary plus 1 degree C”

This page restates published guidance from the sources above and is general information, not medical advice for your baby; your care team’s instructions override it. This page is not medically reviewed and does not diagnose anything. It has no way to tell you your baby is fine. See our editorial standards and corrections · Support numbers, published.