How Do I Take My Baby's Temperature Correctly?
Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist
Content reviewed against published AAP, Mayo Clinic, CDC guidelines
Last reviewed:
If your baby has been diagnosed with or you suspect how do i take my baby's temperature correctly, here is what the evidence says.
The short answer
Rectal temperature is the gold standard for babies under 3 months and the most accurate method for all infants. A rectal temperature of 100.4°F (38°C) or higher is considered a fever. Temporal artery (forehead) and tympanic (ear) thermometers can be used in older babies but are less accurate in very young infants.
Key takeaways
- Rectal temperature is the gold standard for babies under 3 months and the most accurate method for all infants. A rectal temperature of 100.4°F (38°C) or higher is considered a fever. Temporal artery (forehead) and tympanic (ear) thermometers can be used in older babies but are less accurate in very young infants.
- Usually normal when: A slight temperature variation of 0.5-1°F throughout the day, with higher readings in the late afternoon
- Call your doctor if: Any rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months old requires immediate medical evaluation
- Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
Parents everywhere have the same worry. You are doing the right thing by looking into it.
What Parents Should Know
According to AAP, Mayo Clinic, CDC guidelines, rectal temperature is the gold standard for babies under 3 months and the most accurate method for all infants. A rectal temperature of 100.4°F (38°C) or higher is considered a fever. Temporal artery (forehead) and tympanic (ear) thermometers can be used in older babies but are less accurate in very young infants. At 0-3 months, rectal temperature is the only recommended method for babies under 3 months because accuracy is critical at this age. A fever of 100.4°F (38°C) or higher in a newborn requires immediate medical evaluation. Use a digital rectal thermometer with petroleum jelly on the tip, insert gently about half an inch, and hold in place until it beeps. Never use a glass mercury thermometer. It is generally considered normal when a slight temperature variation of 0.5-1°F throughout the day, with higher readings in the late afternoon. However, you should contact your pediatrician promptly if any rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months old requires immediate medical evaluation.
Normal vs. Concerning
By Age
What to expect by age
0-3 months
Rectal temperature is the only recommended method for babies under 3 months because accuracy is critical at this age. A fever of 100.4°F (38°C) or higher in a newborn requires immediate medical evaluation. Use a digital rectal thermometer with petroleum jelly on the tip, insert gently about half an inch, and hold in place until it beeps. Never use a glass mercury thermometer.
3-6 months
Rectal temperature remains the most accurate method, though temporal artery (forehead) thermometers can be used as a screening tool. If a forehead reading suggests fever, confirm with a rectal temperature. Axillary (underarm) temperature can screen but may read 1-2 degrees lower than actual core temperature. Always report the method used when calling your pediatrician.
6-12 months
You can now use temporal artery, tympanic (ear), or rectal thermometers. Ear thermometers are generally reliable after 6 months but can give inaccurate readings if there is earwax buildup or an ear infection. Forehead thermometers are convenient and reasonably accurate for this age. For the most precise reading, rectal remains best.
12-24 months
Multiple methods work well at this age. Many parents prefer temporal artery thermometers for convenience and less distress. Ear thermometers are also reliable. Rectal is still the most accurate but may be harder with an active toddler. Oral thermometers are not yet recommended as toddlers cannot hold them properly under their tongue.
2-3 years
Temporal artery and ear thermometers work well for toddlers. Some children this age may begin to cooperate with oral thermometers, but most do better with forehead or ear readings. Consistent use of the same method helps you track temperature trends. Always tell your doctor which method you used when reporting a temperature.
What to Tell Your Pediatrician
- Describe when you first noticed how do i take my baby's temperature correctly and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if you are unsure which thermometer method is best for your baby's age.
- Mention if your thermometer gives inconsistent readings and you want guidance on technique.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- A slight temperature variation of 0.5-1°F throughout the day, with higher readings in the late afternoon
- Temperature readings differ slightly between methods (underarm may read lower, rectal may read slightly higher)
- A brief temperature rise after bundling, physical activity, or a warm bath
- Your baby feels warm but the thermometer reads below 100.4°F rectally
- You are unsure which thermometer method is best for your baby's age
- Your thermometer gives inconsistent readings and you want guidance on technique
- Your baby's temperature seems elevated but you are not sure if it is accurate
- Any rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months old requires immediate medical evaluation
- A temperature of 104°F (40°C) or higher at any age, or any fever with lethargy, rash, difficulty breathing, or refusal to feed
What You Can Do at Home
- Keep track of when you notice how do i take my baby's temperature correctly — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that a slight temperature variation of 0.5-1°F throughout the day, with higher readings in the late afternoon — this is generally within the range of normal.
- At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
- While monitoring at home, seek immediate care if any rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months old requires immediate medical evaluation.
Related Conditions
Should I Give Acetaminophen or Ibuprofen for Fever?
Acetaminophen (Tylenol) can be used from birth (with doctor guidance for babies under 3 months), while ibuprofen (Motrin/Advil) is only safe after 6 months of age. Both are effective fever reducers. Acetaminophen works for about 4-6 hours and ibuprofen for 6-8 hours. Always dose by weight, not age, and use the measuring device that comes with the medicine.
Baby Has a High Fever Over 104 Degrees F
A fever above 104 degrees F (40 degrees C) in a baby or toddler can be alarming, but the height of the fever alone does not necessarily indicate a more serious illness. Many common childhood viral infections (like roseola) can cause high fevers. What matters more than the number is how your child looks and behaves. A child with a 104 degree F fever who is still alert, making eye contact, and drinking fluids is less concerning than a child with a 102 degree F fever who is limp and unresponsive. However, fevers above 104 degrees F should always be discussed with your pediatrician.
Managing Fever Without Medication
Fever is the body's natural defense against infection, and not every fever needs medication. For babies over 3 months with low-grade fevers who are otherwise comfortable, non-medication strategies like keeping them lightly dressed, offering extra fluids, and maintaining a comfortable room temperature can be effective. The goal of fever management is comfort, not achieving a specific number on the thermometer.
Related Resources
Fever Decision Tree
Step-by-step guidance for evaluating your baby's fever by age and temperature.
Month-by-Month Development
Detailed monthly development guides from birth through 24 months.
When to Call the Doctor
General guide on when to call the pediatrician, visit urgent care, or go to the ER.
Frequently asked questions
Is how do i take my baby's temperature correctly normal?
When should I call the doctor about how do i take my baby's temperature correctly?
When is how do i take my baby's temperature correctly normal?
What causes how do i take my baby's temperature correctly?
What should I mention to my pediatrician about how do i take my baby's temperature correctly?
Is how do i take my baby's temperature correctly normal at 0-3 months?
Is how do i take my baby's temperature correctly normal at 3-6 months?
Should I go to the ER for how do i take my baby's temperature correctly?
Does how do i take my baby's temperature correctly go away on its own?
References
- [1]American Academy of Pediatrics. How to Take a Child's Temperature. HealthyChildren.org. AAP
- [2]Mayo Clinic. Thermometers: Understand the options. Mayo Clinic
- [3]Centers for Disease Control and Prevention. Fever or Chills. When to Seek Emergency Care. CDC
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss How Do I Take My Baby's Temperature Correctly?.
Things to mention
- Describe when you first noticed how do i take my baby's temperature correctly and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if you are unsure which thermometer method is best for your baby's age.
- Mention if your thermometer gives inconsistent readings and you want guidance on technique.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- You are unsure which thermometer method is best for your baby's age
- Your thermometer gives inconsistent readings and you want guidance on technique
- Your baby's temperature seems elevated but you are not sure if it is accurate
Urgent signs to report immediately
- Any rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months old requires immediate medical evaluation
- A temperature of 104°F (40°C) or higher at any age, or any fever with lethargy, rash, difficulty breathing, or refusal to feed
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members
Related Resources
Bottom line
Most cases of how do i take my baby's temperature correctly are normal. Talk to your pediatrician if any rectal temperature of 100.4°f (38°c) or higher in a baby under 3 months old requires immediate medical evaluation.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
Was this page helpful?
Related Medical Concerns
Should I Give Acetaminophen or Ibuprofen for Fever?
Acetaminophen (Tylenol) can be used from birth (with doctor guidance for babies under 3 months), while ibuprofen (Motrin/Advil) is only safe after 6 months of age. Both are effective fever reducers. Acetaminophen works for about 4-6 hours and ibuprofen for 6-8 hours. Always dose by weight, not age, and use the measuring device that comes with the medicine.
Baby Has a High Fever Over 104 Degrees F
A fever above 104 degrees F (40 degrees C) in a baby or toddler can be alarming, but the height of the fever alone does not necessarily indicate a more serious illness. Many common childhood viral infections (like roseola) can cause high fevers. What matters more than the number is how your child looks and behaves. A child with a 104 degree F fever who is still alert, making eye contact, and drinking fluids is less concerning than a child with a 102 degree F fever who is limp and unresponsive. However, fevers above 104 degrees F should always be discussed with your pediatrician.
Managing Fever Without Medication
Fever is the body's natural defense against infection, and not every fever needs medication. For babies over 3 months with low-grade fevers who are otherwise comfortable, non-medication strategies like keeping them lightly dressed, offering extra fluids, and maintaining a comfortable room temperature can be effective. The goal of fever management is comfort, not achieving a specific number on the thermometer.
My Baby's Head Shape Looks Abnormal
Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.
Achondroplasia (Dwarfism) in Babies
Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.
Adenoid Hypertrophy and Breathing
Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.